patch 9.1.0749: filetype: http files not recognized

Problem:  filetype: http files not recognized
Solution: detect '*.http' as http filetype, include
          http filetype plugin (Riley Bruins)

Based on the specification found
[here](https://github.com/JetBrains/http-request-in-editor-spec/blob/master/spec.md)

closes: #15762

Signed-off-by: Riley Bruins <ribru17@hotmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>

runtime/ftplugin/http.vim

@@ -0,0 +1,13 @@
+" Vim filetype plugin
+" Language:	HTTP
+" Maintainer:	Riley Bruins <ribru17@gmail.com>
+" Last Change:	2024 Sep 28
+
+if exists('b:did_ftplugin')
+  finish
+endif
+let b:did_ftplugin = 1
+
+setl comments=:# commentstring=#\ %s
+
+let b:undo_ftplugin = 'setl com< cms<'