Add requirements for external mixers
Add requirements for external mixers

vrs01/mopidy,bacontext/mopidy,adamcik/mopidy,quartz55/mopidy,ali/mopidy,woutervanwijk/mopidy,diandiankan/mopidy,kingosticks/mopidy,priestd09/mopidy,vrs01/mopidy,hkariti/mopidy,vrs01/mopidy,dbrgn/mopidy,adamcik/mopidy,bacontext/mopidy,abarisain/mopidy,hkariti/mopidy,priestd09/mopidy,liamw9534/mopidy,ZenithDK/mopidy,kingosticks/mopidy,bencevans/mopidy,mopidy/mopidy,glogiotatidis/mopidy,dbrgn/mopidy,woutervanwijk/mopidy,jcass77/mopidy,mokieyue/mopidy,diandiankan/mopidy,jcass77/mopidy,tkem/mopidy,glogiotatidis/mopidy,mopidy/mopidy,SuperStarPL/mopidy,rawdlite/mopidy,adamcik/mopidy,vrs01/mopidy,jmarsik/mopidy,quartz55/mopidy,SuperStarPL/mopidy,liamw9534/mopidy,swak/mopidy,bencevans/mopidy,bencevans/mopidy,pacificIT/mopidy,swak/mopidy,ZenithDK/mopidy,rawdlite/mopidy,quartz55/mopidy,bacontext/mopidy,rawdlite/mopidy,tkem/mopidy,jmarsik/mopidy,dbrgn/mopidy,tkem/mopidy,pacificIT/mopidy,ZenithDK/mopidy,mokieyue/mopidy,jcass77/mopidy,jodal/mopidy,hkariti/mopidy,dbrgn/mopidy,mopidy/mopidy,jmarsik/mopidy,kingosticks/mopidy,abarisain/mopidy,quartz55/mopidy,ZenithDK/mopidy,glogiotatidis/mopidy,swak/mopidy,pacificIT/mopidy,diandiankan/mopidy,diandiankan/mopidy,bencevans/mopidy,bacontext/mopidy,hkariti/mopidy,tkem/mopidy,ali/mopidy,jmarsik/mopidy,swak/mopidy,mokieyue/mopidy,SuperStarPL/mopidy,glogiotatidis/mopidy,ali/mopidy,jodal/mopidy,SuperStarPL/mopidy,priestd09/mopidy,rawdlite/mopidy,mokieyue/mopidy,ali/mopidy,pacificIT/mopidy,jodal/mopidy