Update plugins.md
Update plugins.md

Adding link to new Leaflet.GeographPhotos for displaying Geograph Photos of Britain and Ireland
CapeSepias/Leaflet,CapeSepias/Leaflet,stefanocudini/Leaflet,Leaflet/Leaflet,CapeSepias/Leaflet,stefanocudini/Leaflet,stefanocudini/Leaflet,Leaflet/Leaflet,Leaflet/Leaflet