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/ftplugin/fga.vim

@@ -0,0 +1,13 @@
+" Vim filetype plugin
+" Language:	FGA
+" Maintainer:	Riley Bruins <ribru17@gmail.com>
+" Last Change:	2025 Jul 14
+
+if exists('b:did_ftplugin')
+  finish
+endif
+let b:did_ftplugin = 1
+
+setl comments=:# commentstring=#\ %s
+
+let b:undo_ftplugin = 'setl com< cms<'