vim-patch:9.1.1548: filetype: OpenFGA files are not recognized

Problem:  filetype: OpenFGA files are not recognized
Solution: detect *.fga files as fga filetype, include an fga filetype
          plugin (Riley Bruins)

References:
https://github.com/openfga
https://marketplace.visualstudio.com/items?itemName=openfga.openfga-vscode

closes: vim/vim#17752

0992f62fc1

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

runtime/lua/vim/filetype.lua

@@ -459,6 +459,7 @@ local extension = {
   fwt = 'fan',
   lib = 'faust',
   fnl = 'fennel',
+  fga = 'fga',
   m4gl = 'fgl',
   ['4gl'] = 'fgl',
   ['4gh'] = 'fgl',