vim-patch:9.1.2062: filetype: djot files are not recognized

Problem:  filetype: djot files are not recognized
Solution: Detect *.dj and *.djot files as djot filetype
          (Hoang Nguyen).

Reference:
- https://djot.net/

closes: vim/vim#19105

8d0fcff002

Co-authored-by: Hoang Nguyen <folliekazetani@protonmail.com>

runtime/lua/vim/filetype.lua

@@ -404,6 +404,8 @@ local extension = {
   dhall = 'dhall',
   diff = 'diff',
   rej = 'diff',
+  dj = 'djot',
+  djot = 'djot',
   Dockerfile = 'dockerfile',
   dockerfile = 'dockerfile',
   bat = 'dosbatch',

test/old/testdir/test_filetype.vim

@@ -242,6 +242,7 @@ func s:GetFilenameChecks() abort
     \ 'dictdconf': ['dictd.conf', 'dictdfile.conf', 'dictd-file.conf'],
     \ 'diff': ['file.diff', 'file.rej'],
     \ 'dircolors': ['.dir_colors', '.dircolors', '/etc/DIR_COLORS', 'any/etc/DIR_COLORS'],
+    \ 'djot': ['file.dj', 'file.djot'],
     \ 'dnsmasq': ['/etc/dnsmasq.conf', '/etc/dnsmasq.d/file', 'any/etc/dnsmasq.conf', 'any/etc/dnsmasq.d/file'],
     \ 'dockerfile': ['Containerfile', 'Dockerfile', 'dockerfile', 'file.Dockerfile', 'file.dockerfile', 'Dockerfile.debian', 'Containerfile.something'],
     \ 'dosbatch': ['file.bat'],