Update runtime files

runtime/ftplugin/nroff.vim

@@ -1,7 +1,9 @@
 " Vim filetype plugin
 " Language:	roff(7)
-" Maintainer:	Chris Spiegel <cspiegel@gmail.com>
-" Last Change:	2019 Apr 24
+" Maintainer:	Aman Verma
+" Homepage:	https://github.com/a-vrma/vim-nroff-ftplugin
+" Previous Maintainer:	Chris Spiegel <cspiegel@gmail.com>
+" Last Change:	2020 Nov 21
 
 if exists("b:did_ftplugin")
   finish
@@ -9,3 +11,7 @@ endif
 let b:did_ftplugin = 1
 
 setlocal commentstring=.\\\"%s
+setlocal comments=:.\\\"
+setlocal sections+=Sh
+
+let b:undo_ftplugin = 'setlocal commentstring< comments< sections<'