Add note about .gitignore/.npmignore to plugin guide
Add note about .gitignore/.npmignore to plugin guide

msiadak/Leaflet,iOffice/Leaflet,stefanocudini/Leaflet,davojta/Leaflet,sisou/Leaflet,rlugojr/Leaflet,AP-whitehat/Leaflet,scaddenp/Leaflet,sisou/Leaflet,akrzyzanowskino/TeamSE,nathancahill/Leaflet,tsantacruz/RotationalMarker,tsantacruz/RotationalMarker,bbecquet/Leaflet,Neorth/Leaflet,hyperknot/Leaflet,bbecquet/Leaflet,rlugojr/Leaflet,scaddenp/Leaflet,Leaflet/Leaflet,jblarsen/Leaflet,rlugojr/Leaflet,CapeSepias/Leaflet,iOffice/Leaflet,davojta/Leaflet,sisou/Leaflet,Ubisense/Leaflet,CapeSepias/Leaflet,hyperknot/Leaflet,fab1an/Leaflet,bbecquet/Leaflet,jblarsen/Leaflet,AP-whitehat/Leaflet,frogcat/Leaflet,jasonoverland/Leaflet,w8r/Leaflet,Trufi/Leaflet,codeator/Leaflet,jasonoverland/Leaflet,w8r/Leaflet,AP-whitehat/Leaflet,fab1an/Leaflet,Leaflet/Leaflet,fab1an/Leaflet,Ubisense/Leaflet,jasonoverland/Leaflet,Trufi/Leaflet,geoloep/Leaflet,Neorth/Leaflet,brah/Leaflet,iZucken/Leaflet,nathancahill/Leaflet,geoloep/Leaflet,brah/Leaflet,geoloep/Leaflet,stefanocudini/Leaflet,Trufi/Leaflet,Neorth/Leaflet,msiadak/Leaflet,jblarsen/Leaflet,scaddenp/Leaflet,hyperknot/Leaflet,Leaflet/Leaflet,brah/Leaflet,iOffice/Leaflet,codeator/Leaflet,tsantacruz/RotationalMarker,msiadak/Leaflet,w8r/Leaflet,CapeSepias/Leaflet,nathancahill/Leaflet,davojta/Leaflet,frogcat/Leaflet,akrzyzanowskino/TeamSE,akrzyzanowskino/TeamSE,Ubisense/Leaflet,iZucken/Leaflet,iZucken/Leaflet,stefanocudini/Leaflet,frogcat/Leaflet,codeator/Leaflet