vim-patch:9.1.0303: filetype: some protocol buffer files not recognized (#28293)

Problem:  filetype: some protocol buffer files not recognized
Solution: Detect '*.textproto', '*.textpb', '*.txtpb' as pbtxt files
          (Bruno Belanyi)

See: https://protobuf.dev/reference/protobuf/textformat-spec/#text-format-files

closes: vim/vim#14463

e54a8e7c73

Co-authored-by: Bruno BELANYI <bruno@belanyi.fr>

runtime/lua/vim/filetype.lua

@@ -776,6 +776,9 @@ local extension = {
   pas = 'pascal',
   lpr = detect_line1('<%?xml', 'xml', 'pascal'),
   dpr = 'pascal',
+  txtpb = 'pbtxt',
+  textproto = 'pbtxt',
+  textpb = 'pbtxt',
   pbtxt = 'pbtxt',
   g = 'pccts',
   pcmk = 'pcmk',