Add information about official plugins to :h intro.
Add information about official plugins to :h intro.

Update issue 315
There you go.

madand/pentadactyl-pm,airodactyl/dactyl,moonshadow/dactyl,invl/dactyl,5digits/dactyl,nathyong/dactyl,airodactyl/dactyl,madand/pentadactyl-pm,invl/dactyl,airodactyl/dactyl,airodactyl/dactyl,Kjwon15/dactyl,Kjwon15/dactyl,moonshadow/dactyl,airodactyl/dactyl,invl/dactyl,airodactyl/dactyl,invl/dactyl,madand/pentadactyl-pm,Kjwon15/dactyl,nathyong/dactyl,madand/pentadactyl-pm,5digits/dactyl,Kjwon15/dactyl,moonshadow/dactyl,moonshadow/dactyl,nathyong/dactyl,nathyong/dactyl,5digits/dactyl,5digits/dactyl,invl/dactyl,Kjwon15/dactyl,Kjwon15/dactyl,invl/dactyl,5digits/dactyl,nathyong/dactyl,moonshadow/dactyl,madand/pentadactyl-pm,5digits/dactyl,moonshadow/dactyl,nathyong/dactyl,madand/pentadactyl-pm