vim-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: vim/vim#15762

de6c1d1182

Co-authored-by: Riley Bruins <ribru17@hotmail.com>

runtime/lua/vim/filetype.lua

@@ -578,6 +578,7 @@ local extension = {
   stm = detect.html,
   htt = 'httest',
   htb = 'httest',
+  http = 'http',
   hurl = 'hurl',
   hw = detect.hw,
   module = detect.hw,