patch 9.1.1501: filetype: flix files are not recognized

Problem:  filetype: flix files are not recognized
Solution: detect *.flix files as flix filetype
          (0xadk)

References:
- https://flix.dev/
- https://doc.flix.dev/introduction.html

closes: #17646

Signed-off-by: 0xadk <0xadk@users.noreply.github.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>

runtime/filetype.vim

@@ -893,6 +893,9 @@ au BufNewFile,BufRead *.fish			setf fish
 " Flatpak config
 au BufNewFile,BufRead */flatpak/repo/config	setf dosini
 
+" Flix
+au BufNewFile,BufRead *.flix			setf flix
+
 " Focus Executable
 au BufNewFile,BufRead *.fex,*.focexec		setf focexec