vim-patch:8.2.3374: Pyret files are not recognized (#15642)

Problem:    Pyret files are not recognized.
Solution:   Recognize .arr files as Pyret. (Doug Kearns)
eb05d05f8a

runtime/filetype.vim

@@ -1382,6 +1382,9 @@ au BufNewFile,BufRead *.pk			setf poke
 " Protocols
 au BufNewFile,BufRead */etc/protocols		setf protocols
 
+" Pyret
+au BufNewFile,BufRead *.arr			setf pyret
+
 " Pyrex
 au BufNewFile,BufRead *.pyx,*.pxd		setf pyrex
 

src/nvim/testdir/test_filetype.vim

@@ -398,6 +398,7 @@ let s:filename_checks = {
     \ 'psf': ['file.psf'],
     \ 'psl': ['file.psl'],
     \ 'puppet': ['file.pp'],
+    \ 'pyret': ['file.arr'],
     \ 'pyrex': ['file.pyx', 'file.pxd'],
     \ 'python': ['file.py', 'file.pyw', '.pythonstartup', '.pythonrc', 'file.ptl', 'file.pyi', 'SConstruct'],
     \ 'quake': ['anybaseq2/file.cfg', 'anyid1/file.cfg', 'quake3/file.cfg', 'baseq2/file.cfg', 'id1/file.cfg', 'quake1/file.cfg', 'some-baseq2/file.cfg', 'some-id1/file.cfg', 'some-quake1/file.cfg'],