vim-patch:9.1.1909: filetype: .mom files recognized as nroff files (#36543)

Problem:  filetype: .mom files recognized as nroff files
Solution: Detect *.mom files as groff filetype instead
          (Callum Andrew)

Reference:
- mom macros are written specifically for groff:
  https://www.schaffter.ca/mom/

closes: vim/vim#18718

23e12c0b7e

Co-authored-by: Callum Andrew <dev@candrew.net>

runtime/lua/vim/filetype.lua

@@ -549,6 +549,8 @@ local extension = {
   graphql = 'graphql',
   graphqls = 'graphql',
   gretl = 'gretl',
+  groff = 'groff',
+  mom = 'groff',
   gradle = 'groovy',
   groovy = 'groovy',
   gsp = 'gsp',
@@ -874,7 +876,6 @@ local extension = {
   roff = 'nroff',
   tmac = 'nroff',
   man = 'nroff',
-  mom = 'nroff',
   nr = 'nroff',
   tr = 'nroff',
   nsi = 'nsis',

test/old/testdir/test_filetype.vim

@@ -343,6 +343,7 @@ func s:GetFilenameChecks() abort
     \ 'grads': ['file.gs'],
     \ 'graphql': ['file.graphql', 'file.graphqls', 'file.gql'],
     \ 'gretl': ['file.gretl'],
+    \ 'groff': ['file.groff', 'file.mom'],
     \ 'groovy': ['file.gradle', 'file.groovy', 'Jenkinsfile'],
     \ 'group': ['any/etc/group', 'any/etc/group-', 'any/etc/group.edit', 'any/etc/gshadow', 'any/etc/gshadow-', 'any/etc/gshadow.edit', 'any/var/backups/group.bak', 'any/var/backups/gshadow.bak', '/etc/group', '/etc/group-', '/etc/group.edit', '/etc/gshadow', '/etc/gshadow-', '/etc/gshadow.edit', '/var/backups/group.bak', '/var/backups/gshadow.bak'],
     \ 'grub': ['/boot/grub/menu.lst', '/boot/grub/grub.conf', '/etc/grub.conf', 'any/boot/grub/grub.conf', 'any/boot/grub/menu.lst', 'any/etc/grub.conf'],
@@ -573,7 +574,7 @@ func s:GetFilenameChecks() abort
     \ 'nix': ['file.nix'],
     \ 'norg': ['file.norg'],
     \ 'nqc': ['file.nqc'],
-    \ 'nroff': ['file.tr', 'file.nr', 'file.roff', 'file.tmac', 'file.mom', 'tmac.file'],
+    \ 'nroff': ['file.tr', 'file.nr', 'file.roff', 'file.tmac', 'tmac.file'],
     \ 'nsis': ['file.nsi', 'file.nsh'],
     \ 'ntriples': ['file.nt'],
     \ 'nu': ['file.nu'],