Update Map reference docs with baselayerchange
Update Map reference docs with baselayerchange

baselayerchange is a new event that has landed in master, so it needs to be documented for easy reference.
scaddenp/Leaflet,brah/Leaflet,sisou/Leaflet,Leaflet/Leaflet,iOffice/Leaflet,akrzyzanowskino/TeamSE,Neorth/Leaflet,CapeSepias/Leaflet,iOffice/Leaflet,jasonoverland/Leaflet,jasonoverland/Leaflet,frogcat/Leaflet,geoloep/Leaflet,Trufi/Leaflet,codeator/Leaflet,CapeSepias/Leaflet,scaddenp/Leaflet,sisou/Leaflet,codeator/Leaflet,tsantacruz/RotationalMarker,msiadak/Leaflet,sisou/Leaflet,tsantacruz/RotationalMarker,AP-whitehat/Leaflet,msiadak/Leaflet,AP-whitehat/Leaflet,Ubisense/Leaflet,scaddenp/Leaflet,tsantacruz/RotationalMarker,AP-whitehat/Leaflet,Leaflet/Leaflet,stefanocudini/Leaflet,frogcat/Leaflet,Trufi/Leaflet,rlugojr/Leaflet,iZucken/Leaflet,Neorth/Leaflet,jasonoverland/Leaflet,CapeSepias/Leaflet,brah/Leaflet,codeator/Leaflet,geoloep/Leaflet,iZucken/Leaflet,Trufi/Leaflet,rlugojr/Leaflet,Ubisense/Leaflet,stefanocudini/Leaflet,akrzyzanowskino/TeamSE,Leaflet/Leaflet,davojta/Leaflet,msiadak/Leaflet,davojta/Leaflet,akrzyzanowskino/TeamSE,Ubisense/Leaflet,iZucken/Leaflet,davojta/Leaflet,brah/Leaflet,rlugojr/Leaflet,geoloep/Leaflet,frogcat/Leaflet,iOffice/Leaflet,Neorth/Leaflet,stefanocudini/Leaflet