makefiles:docker.inc.mk: add a global documentation on directory mapping
makefiles:docker.inc.mk: add a global documentation on directory mapping

RIOT-OS/RIOT,basilfx/RIOT,aeneby/RIOT,ant9000/RIOT,rfuentess/RIOT,mfrey/RIOT,cladmi/RIOT,kaspar030/RIOT,ant9000/RIOT,authmillenon/RIOT,mtausig/RIOT,yogo1212/RIOT,lazytech-org/RIOT,kYc0o/RIOT,smlng/RIOT,mfrey/RIOT,ant9000/RIOT,rfuentess/RIOT,A-Paul/RIOT,smlng/RIOT,mfrey/RIOT,jasonatran/RIOT,aeneby/RIOT,josephnoir/RIOT,yogo1212/RIOT,jasonatran/RIOT,A-Paul/RIOT,OlegHahm/RIOT,jasonatran/RIOT,toonst/RIOT,RIOT-OS/RIOT,smlng/RIOT,A-Paul/RIOT,A-Paul/RIOT,toonst/RIOT,RIOT-OS/RIOT,aeneby/RIOT,A-Paul/RIOT,mfrey/RIOT,OlegHahm/RIOT,kaspar030/RIOT,mtausig/RIOT,rfuentess/RIOT,cladmi/RIOT,kYc0o/RIOT,OTAkeys/RIOT,yogo1212/RIOT,basilfx/RIOT,mtausig/RIOT,miri64/RIOT,josephnoir/RIOT,josephnoir/RIOT,x3ro/RIOT,kYc0o/RIOT,OTAkeys/RIOT,lazytech-org/RIOT,mtausig/RIOT,miri64/RIOT,authmillenon/RIOT,aeneby/RIOT,miri64/RIOT,mtausig/RIOT,kaspar030/RIOT,OlegHahm/RIOT,OTAkeys/RIOT,authmillenon/RIOT,toonst/RIOT,authmillenon/RIOT,mfrey/RIOT,smlng/RIOT,miri64/RIOT,jasonatran/RIOT,yogo1212/RIOT,kaspar030/RIOT,josephnoir/RIOT,toonst/RIOT,cladmi/RIOT,authmillenon/RIOT,lazytech-org/RIOT,x3ro/RIOT,kYc0o/RIOT,kYc0o/RIOT,kaspar030/RIOT,OlegHahm/RIOT,basilfx/RIOT,toonst/RIOT,RIOT-OS/RIOT,x3ro/RIOT,yogo1212/RIOT,authmillenon/RIOT,miri64/RIOT,jasonatran/RIOT,cladmi/RIOT,yogo1212/RIOT,ant9000/RIOT,RIOT-OS/RIOT,josephnoir/RIOT,ant9000/RIOT,basilfx/RIOT,x3ro/RIOT,smlng/RIOT,cladmi/RIOT,aeneby/RIOT,lazytech-org/RIOT,rfuentess/RIOT,rfuentess/RIOT,basilfx/RIOT,OlegHahm/RIOT,OTAkeys/RIOT,x3ro/RIOT,lazytech-org/RIOT,OTAkeys/RIOT