patch 9.0.2060: *.{gn,gni} files are not recognized

Problem:  *.{gn,gni} files are not recognized
Solution: Detect some as gn filetype (without adding an extra filetype)

Those come from: https://gn.googlesource.com/gn/

closes: #13405

Signed-off-by: Christian Brabandt <cb@256bit.org>
Co-authored-by: Amaan Qureshi <amaanq12@gmail.com>

runtime/filetype.vim

@@ -818,6 +818,9 @@ au BufNewFile,BufRead *.gleam			setf gleam
 " GLSL
 au BufNewFile,BufRead *.glsl			setf glsl
 
+" GN (generate ninja) files
+au BufNewFile,BufRead *.gn,*.gni		setf gn
+
 " GP scripts (2.0 and onward)
 au BufNewFile,BufRead *.gp,.gprc		setf gp
 

src/testdir/test_filetype.vim

@@ -277,6 +277,7 @@ def s:GetFilenameChecks(): dict<list<string>>
     gkrellmrc: ['gkrellmrc', 'gkrellmrc_x'],
     gleam: ['file.gleam'],
     glsl: ['file.glsl'],
+    gn: ['file.gn', 'file.gni'],
     gnash: ['gnashrc', '.gnashrc', 'gnashpluginrc', '.gnashpluginrc'],
     gnuplot: ['file.gpi', '.gnuplot'],
     go: ['file.go'],

src/version.c

@@ -704,6 +704,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    2060,
 /**/
     2059,
 /**/