docs: Add Mopidy-SoftwareMixer to the mixer impl list
docs: Add Mopidy-SoftwareMixer to the mixer impl list

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