Runtime: add new sed ftplugin (#12843)

.github/CODEOWNERS

@@ -207,6 +207,7 @@ runtime/ftplugin/sass.vim		@tpope
 runtime/ftplugin/scala.vim		@derekwyatt
 runtime/ftplugin/scss.vim		@tpope
 runtime/ftplugin/sdoc.vim		@gpanders
+runtime/ftplugin/sed.vim		@dkearns
 runtime/ftplugin/sh.vim			@dkearns
 runtime/ftplugin/solution.vim		@dkearns
 runtime/ftplugin/spec.vim		@ignatenkobrain

runtime/ftplugin/sed.vim

@@ -0,0 +1,29 @@
+" Vim filetype plugin file
+" Language:	sed
+" Maintainer:	Doug Kearns <dougkearns@gmail.com>
+" Last Change:	2020 Apr 1
+
+if exists("b:did_ftplugin")
+    finish
+endif
+let b:did_ftplugin = 1
+
+let s:cpo_save = &cpo
+set cpo&vim
+
+setlocal comments=:#
+setlocal commentstring=#\ %s
+setlocal formatoptions-=t formatoptions+=croql
+
+let b:undo_ftplugin = "setl com< cms< fo<"
+
+if (has("gui_win32") || has("gui_gtk")) && !exists("b:browsefilter")
+  let b:browsefilter = "sed Script Files (*.sed)\t*.sed\n" ..
+	\	       "All Files (*.*)\t*.*\n"
+  let b:undo_ftplugin ..= " | unlet! b:browsefilter"
+endif
+
+let &cpo = s:cpo_save
+unlet s:cpo_save
+
+" vim: nowrap sw=2 sts=2 ts=8