patch 8.2.3283: Julia filetype is not recognized

Problem:    Julia filetype is not recognized
Solution:   Add filetype detection. (Christian Clason, closes #8700)

runtime/filetype.vim

@@ -874,6 +874,9 @@ au BufNewFile,BufRead *.ipynb				setf json
 " JSONC
 au BufNewFile,BufRead *.jsonc			setf jsonc
 
+" Julia
+au BufNewFile,BufRead *.jl			setf julia
+
 " Kixtart
 au BufNewFile,BufRead *.kix			setf kix
 

src/testdir/test_filetype.vim

@@ -263,6 +263,7 @@ let s:filename_checks = {
     \ 'json': ['file.json', 'file.jsonp', 'file.json-patch', 'file.webmanifest', 'Pipfile.lock', 'file.ipynb'],
     \ 'jsonc': ['file.jsonc'],
     \ 'jsp': ['file.jsp'],
+    \ 'julia': ['file.jl'],
     \ 'kconfig': ['Kconfig', 'Kconfig.debug', 'Kconfig.file'],
     \ 'kivy': ['file.kv'],
     \ 'kix': ['file.kix'],
@@ -778,6 +779,7 @@ func Test_pp_file()
   split Xfile.pp
   call assert_equal('pascal', &filetype)
   bwipe!
+  unlet g:filetype_pp
 
   " Test dist#ft#FTpp()
   call writefile(['{ pascal comment'], 'Xfile.pp')

src/version.c

@@ -755,6 +755,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    3283,
 /**/
     3282,
 /**/