Add note how to use requirements.txt
Add note how to use requirements.txt

We want to use (apparently) requirements.txt to store mbed's Python package dependencies.
Users can use this file with pip to install those requirements.

NXPmicro/mbed,rosterloh/mbed,jeremybrodt/mbed,nRFMesh/mbed-os,NXPmicro/mbed,screamerbg/mbed,jrjang/mbed,betzw/mbed-os,al177/mbed,pi19404/mbed,brstew/MBED-BUILD,bentwire/mbed,mazimkhan/mbed-os,jferreir/mbed,bentwire/mbed,adamgreen/mbed,pbrook/mbed,kl-cruz/mbed-os,adustm/mbed,betzw/mbed-os,Shengliang/mbed,Timmmm/mbed,nabilbendafi/mbed,maximmbed/mbed,andcor02/mbed-os,andreaslarssonublox/mbed,svogl/mbed-os,CalSol/mbed,karsev/mbed-os,screamerbg/mbed,bentwire/mbed,karsev/mbed-os,andreaslarssonublox/mbed,bulislaw/mbed-os,maximmbed/mbed,mikaleppanen/mbed-os,devanlai/mbed,mnlipp/mbed,andreaslarssonublox/mbed,mazimkhan/mbed-os,nvlsianpu/mbed,fanghuaqi/mbed,jrjang/mbed,svogl/mbed-os,tung7970/mbed-os-1,CalSol/mbed,adustm/mbed,jeremybrodt/mbed,pbrook/mbed,hwfwgrp/mbed,mikaleppanen/mbed-os,monkiineko/mbed-os,ARM-software/mbed-beetle,fpiot/mbed-ats,jferreir/mbed,betzw/mbed-os,al177/mbed,nvlsianpu/mbed,nvlsianpu/mbed,svogl/mbed-os,Timmmm/mbed,andcor02/mbed-os,netzimme/mbed-os,NXPmicro/mbed,pi19404/mbed,jpbrucker/mbed,Timmmm/mbed,cvtsi2sd/mbed-os,mmorenobarm/mbed-os,karsev/mbed-os,YarivCol/mbed-os,bcostm/mbed-os,kl-cruz/mbed-os,rgrover/mbed,jpbrucker/mbed,fahhem/mbed-os,brstew/MBED-BUILD,nRFMesh/mbed-os,arostm/mbed-os,tung7970/mbed-os,andcor02/mbed-os,bentwire/mbed,mmorenobarm/mbed-os,geky/mbed,fanghuaqi/mbed,kl-cruz/mbed-os,j-greffe/mbed-os,fvincenzo/mbed-os,nvlsianpu/mbed,Timmmm/mbed,jrjang/mbed,fpiot/mbed-ats,Shengliang/mbed,NXPmicro/mbed,c1728p9/mbed-os,cvtsi2sd/mbed-os,fahhem/mbed-os,nvlsianpu/mbed,autopulated/mbed,Tiryoh/mbed,theotherjimmy/mbed,j-greffe/mbed-os,Timmmm/mbed,masaohamanaka/mbed,fahhem/mbed-os,Tiryoh/mbed,DanKupiniak/mbed,CalSol/mbed,YarivCol/mbed-os,tung7970/mbed-os,kpurusho/mbed,tung7970/mbed-os-1,bentwire/mbed,svastm/mbed,EmuxEvans/mbed,j-greffe/mbed-os,hwfwgrp/mbed,infinnovation/mbed-os,al177/mbed,mbedmicro/mbed,jpbrucker/mbed,masaohamanaka/mbed,svastm/mbed,catiedev/mbed-os,c1728p9/mbed-os,jeremybrodt/mbed,fpiot/mbed-ats,nRFMesh/mbed-os,brstew/MBED-BUILD,nabilbendafi/mbed,andcor02/mbed-os,karsev/mbed-os,rgrover/mbed,karsev/mbed-os,autopulated/mbed,andreaslarssonublox/mbed,HeadsUpDisplayInc/mbed,ARM-software/mbed-beetle,radhika-raghavendran/mbed-os5.1-onsemi,netzimme/mbed-os,radhika-raghavendran/mbed-os5.1-onsemi,mnlipp/mbed,Shengliang/mbed,al177/mbed,bulislaw/mbed-os,svastm/mbed,RonEld/mbed,masaohamanaka/mbed,infinnovation/mbed-os,cvtsi2sd/mbed-os,jferreir/mbed,mmorenobarm/mbed-os,ryankurte/mbed-os,monkiineko/mbed-os,c1728p9/mbed-os,masaohamanaka/mbed,pbrook/mbed,bikeNomad/mbed,jrjang/mbed,bulislaw/mbed-os,rgrover/mbed,maximmbed/mbed,YarivCol/mbed-os,mbedmicro/mbed,mnlipp/mbed,bulislaw/mbed-os,tung7970/mbed-os,ryankurte/mbed-os,autopulated/mbed,bcostm/mbed-os,maximmbed/mbed,theotherjimmy/mbed,larks/mbed,radhika-raghavendran/mbed-os5.1-onsemi,tung7970/mbed-os-1,bcostm/mbed-os,nRFMesh/mbed-os,cvtsi2sd/mbed-os,hwfwgrp/mbed,mmorenobarm/mbed-os,rosterloh/mbed,pedromes/mbed,j-greffe/mbed-os,dbestm/mbed,geky/mbed,adustm/mbed,rosterloh/mbed,getopenmono/mbed,cvtsi2sd/mbed-os,jeremybrodt/mbed,c1728p9/mbed-os,Archcady/mbed-os,geky/mbed,kl-cruz/mbed-os,adamgreen/mbed,svogl/mbed-os,j-greffe/mbed-os,radhika-raghavendran/mbed-os5.1-onsemi,Archcady/mbed-os,andcor02/mbed-os,theotherjimmy/mbed,brstew/MBED-BUILD,bcostm/mbed-os,arostm/mbed-os,fanghuaqi/mbed,fvincenzo/mbed-os,jpbrucker/mbed,kl-cruz/mbed-os,svastm/mbed,theotherjimmy/mbed,K4zuki/mbed,ryankurte/mbed-os,ryankurte/mbed-os,cvtsi2sd/mbed-os,kpurusho/mbed,EmuxEvans/mbed,Archcady/mbed-os,jpbrucker/mbed,autopulated/mbed,rgrover/mbed,jpbrucker/mbed,radhika-raghavendran/mbed-os5.1-onsemi,HeadsUpDisplayInc/mbed,Tiryoh/mbed,hwfwgrp/mbed,Tiryoh/mbed,K4zuki/mbed,theotherjimmy/mbed,bulislaw/mbed-os,Shengliang/mbed,struempelix/mbed,screamerbg/mbed,hwfwgrp/mbed,andcor02/mbed-os,struempelix/mbed,netzimme/mbed-os,pradeep-gr/mbed-os5-onsemi,mnlipp/mbed,getopenmono/mbed,mmorenobarm/mbed-os,nRFMesh/mbed-os,pedromes/mbed,dbestm/mbed,getopenmono/mbed,pbrook/mbed,ryankurte/mbed-os,struempelix/mbed,pbrook/mbed,maximmbed/mbed,YarivCol/mbed-os,jferreir/mbed,kjbracey-arm/mbed,adustm/mbed,RonEld/mbed,HeadsUpDisplayInc/mbed,tung7970/mbed-os,K4zuki/mbed,rosterloh/mbed,wodji/mbed,geky/mbed,netzimme/mbed-os,dbestm/mbed,mikaleppanen/mbed-os,catiedev/mbed-os,pradeep-gr/mbed-os5-onsemi,monkiineko/mbed-os,fahhem/mbed-os,arostm/mbed-os,EmuxEvans/mbed,RonEld/mbed,fanghuaqi/mbed,theotherjimmy/mbed,dbestm/mbed,adamgreen/mbed,larks/mbed,arostm/mbed-os,Archcady/mbed-os,Archcady/mbed-os,nabilbendafi/mbed,tung7970/mbed-os-1,struempelix/mbed,NXPmicro/mbed,getopenmono/mbed,dbestm/mbed,pi19404/mbed,jferreir/mbed,pedromes/mbed,mikaleppanen/mbed-os,bikeNomad/mbed,struempelix/mbed,autopulated/mbed,Tiryoh/mbed,RonEld/mbed,EmuxEvans/mbed,screamerbg/mbed,infinnovation/mbed-os,adustm/mbed,pedromes/mbed,larks/mbed,bikeNomad/mbed,pradeep-gr/mbed-os5-onsemi,screamerbg/mbed,bentwire/mbed,devanlai/mbed,betzw/mbed-os,masaohamanaka/mbed,kpurusho/mbed,fahhem/mbed-os,NXPmicro/mbed,rosterloh/mbed,DanKupiniak/mbed,HeadsUpDisplayInc/mbed,nabilbendafi/mbed,nvlsianpu/mbed,mikaleppanen/mbed-os,larks/mbed,catiedev/mbed-os,andreaslarssonublox/mbed,mazimkhan/mbed-os,radhika-raghavendran/mbed-os5.1-onsemi,pedromes/mbed,wodji/mbed,mbedmicro/mbed,pedromes/mbed,brstew/MBED-BUILD,ryankurte/mbed-os,pradeep-gr/mbed-os5-onsemi,al177/mbed,c1728p9/mbed-os,monkiineko/mbed-os,catiedev/mbed-os,Shengliang/mbed,svogl/mbed-os,netzimme/mbed-os,pi19404/mbed,al177/mbed,adamgreen/mbed,mikaleppanen/mbed-os,nabilbendafi/mbed,rosterloh/mbed,YarivCol/mbed-os,nabilbendafi/mbed,mazimkhan/mbed-os,karsev/mbed-os,kjbracey-arm/mbed,adustm/mbed,tung7970/mbed-os-1,infinnovation/mbed-os,wodji/mbed,bcostm/mbed-os,j-greffe/mbed-os,mmorenobarm/mbed-os,pradeep-gr/mbed-os5-onsemi,kl-cruz/mbed-os,wodji/mbed,brstew/MBED-BUILD,fvincenzo/mbed-os,catiedev/mbed-os,devanlai/mbed,DanKupiniak/mbed,pbrook/mbed,svogl/mbed-os,Tiryoh/mbed,autopulated/mbed,fanghuaqi/mbed,RonEld/mbed,adamgreen/mbed,YarivCol/mbed-os,K4zuki/mbed,devanlai/mbed,fvincenzo/mbed-os,kjbracey-arm/mbed,DanKupiniak/mbed,CalSol/mbed,devanlai/mbed,jrjang/mbed,monkiineko/mbed-os,tung7970/mbed-os,pradeep-gr/mbed-os5-onsemi,larks/mbed,RonEld/mbed,fpiot/mbed-ats,K4zuki/mbed,netzimme/mbed-os,getopenmono/mbed,catiedev/mbed-os,HeadsUpDisplayInc/mbed,mnlipp/mbed,bulislaw/mbed-os,masaohamanaka/mbed,fpiot/mbed-ats,mbedmicro/mbed,screamerbg/mbed,getopenmono/mbed,Archcady/mbed-os,jrjang/mbed,svastm/mbed,larks/mbed,hwfwgrp/mbed,mbedmicro/mbed,ARM-software/mbed-beetle,nRFMesh/mbed-os,infinnovation/mbed-os,jferreir/mbed,kpurusho/mbed,pi19404/mbed,fahhem/mbed-os,betzw/mbed-os,monkiineko/mbed-os,c1728p9/mbed-os,Shengliang/mbed,maximmbed/mbed,HeadsUpDisplayInc/mbed,wodji/mbed,bikeNomad/mbed,struempelix/mbed,pi19404/mbed,fpiot/mbed-ats,infinnovation/mbed-os,mazimkhan/mbed-os,wodji/mbed,devanlai/mbed,mazimkhan/mbed-os,jeremybrodt/mbed,fvincenzo/mbed-os,arostm/mbed-os,adamgreen/mbed,arostm/mbed-os,kjbracey-arm/mbed,kpurusho/mbed,bikeNomad/mbed,geky/mbed,K4zuki/mbed,kpurusho/mbed,betzw/mbed-os,CalSol/mbed,bcostm/mbed-os,CalSol/mbed,Timmmm/mbed,rgrover/mbed,dbestm/mbed,EmuxEvans/mbed,EmuxEvans/mbed,ARM-software/mbed-beetle,mnlipp/mbed