Update CONTRIBUTING.md
Update CONTRIBUTING.md

Add `help wanted` explain.
DemocraciaEnRed/comunas,AbraaoAlves/app,DemocracyOS/app,DemocraciaEnRed/comunas,moustachu/democracy-os-app,dkrathi457/app,beomjae/app,beomjae/app,DemocraciaEnRed/bahiablanca,atlatszo/evoks,maiklaguna/app,EuParticipo/Caxias,10Pines/app,huulbaek/app,PartidoDeLaRed/app,josuedor/app,vntrp/app,solde9/app,mbhicks90/myvotes.ca,okfn-brasil/euvoto,alexproca/democracy-os,solde9/app,vntrp/app,ManuH/app,120photo/app,ManuH/app,fonorobert/evoks,PartidoDeLaRed/app,ben-pr-p/app,MareAtlantica/democracyos,Nicolas-Lebreton/app,Nicolas-Lebreton/app,indiofran/app,radvansky-tomas/app,moustachu/democracy-os-app,kant/app,ben-pr-p/app,piratenfraktion-nrw/app,120photo/app,EuParticipo/Caxias,dkrathi457/app,MareAtlantica/democracyos,valentinchaput/app,okfn-brasil/euvoto,DemocracyOS/app,CivicTechFR/DemocracyOSFR,CivicTechFR/DemocracyOSFR,piratenfraktion-nrw/app,alexproca/democracy-os,valentinchaput/app,fonorobert/evoks,mgarciaisaia/democracy-os-ues,josuedor/app,huulbaek/app,DemocraciaEnRed/bahiablanca,radvansky-tomas/app,indiofran/app,kant/app,atlatszo/evoks,mbhicks90/myvotes.ca,d-cent/democracyos,AbraaoAlves/app