patch 8.2.4191: json5 files are not recognized

Problem:    json5 files are not recognized.
Solution:   Add a pattern for json5 files. (closes #9601)

runtime/filetype.vim

@@ -888,6 +888,9 @@ au BufNewFile,BufRead *.jov,*.j73,*.jovial	setf jovial
 " JSON
 au BufNewFile,BufRead *.json,*.jsonp,*.webmanifest	setf json
 
+" JSON5
+au BufNewFile,BufRead *.json5			setf json5
+
 " JSON Patch (RFC 6902)
 au BufNewFile,BufRead *.json-patch			setf json
 

src/testdir/test_filetype.vim

@@ -265,6 +265,7 @@ let s:filename_checks = {
     \ 'jovial': ['file.jov', 'file.j73', 'file.jovial'],
     \ 'jproperties': ['file.properties', 'file.properties_xx', 'file.properties_xx_xx', 'some.properties_xx_xx_file'],
     \ 'json': ['file.json', 'file.jsonp', 'file.json-patch', 'file.webmanifest', 'Pipfile.lock', 'file.ipynb', '.babelrc', '.eslintrc', '.prettierrc', '.firebaserc', 'file.slnf'],
+    \ 'json5': ['file.json5'],
     \ 'jsonc': ['file.jsonc'],
     \ 'jsp': ['file.jsp'],
     \ 'julia': ['file.jl'],

src/version.c

@@ -750,6 +750,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    4191,
 /**/
     4190,
 /**/