Add leaflet.latlng-graticule to plugins.md (#4728)
Add leaflet.latlng-graticule to plugins.md (#4728)

* Add a plugin that create a canvas as ImageOverlay to draw the Lat/Lon Graticule, and show the grid tick label at the edges of the map.
msiadak/Leaflet,Leaflet/Leaflet,Ubisense/Leaflet,akrzyzanowskino/TeamSE,geoloep/Leaflet,stefanocudini/Leaflet,frogcat/Leaflet,davojta/Leaflet,scaddenp/Leaflet,sisou/Leaflet,CapeSepias/Leaflet,geoloep/Leaflet,brah/Leaflet,AP-whitehat/Leaflet,Ubisense/Leaflet,Neorth/Leaflet,frogcat/Leaflet,iZucken/Leaflet,codeator/Leaflet,davojta/Leaflet,tsantacruz/RotationalMarker,brah/Leaflet,stefanocudini/Leaflet,frogcat/Leaflet,rlugojr/Leaflet,CapeSepias/Leaflet,brah/Leaflet,scaddenp/Leaflet,jasonoverland/Leaflet,Ubisense/Leaflet,iZucken/Leaflet,rlugojr/Leaflet,jasonoverland/Leaflet,akrzyzanowskino/TeamSE,iZucken/Leaflet,codeator/Leaflet,akrzyzanowskino/TeamSE,msiadak/Leaflet,tsantacruz/RotationalMarker,AP-whitehat/Leaflet,Leaflet/Leaflet,Neorth/Leaflet,Trufi/Leaflet,Leaflet/Leaflet,AP-whitehat/Leaflet,Neorth/Leaflet,sisou/Leaflet,CapeSepias/Leaflet,tsantacruz/RotationalMarker,geoloep/Leaflet,sisou/Leaflet,codeator/Leaflet,scaddenp/Leaflet,rlugojr/Leaflet,Trufi/Leaflet,iOffice/Leaflet,jasonoverland/Leaflet,davojta/Leaflet,Trufi/Leaflet,msiadak/Leaflet,iOffice/Leaflet,stefanocudini/Leaflet,iOffice/Leaflet