vim-patch:9.1.1504: filetype: numbat files are not recognized

Problem:  filetype: numbat files are not recognized
Solution: detect *.nbt files as numbat filetype (0xadk)

References:
- https://github.com/sharkdp/numbat
- https://github.com/sharkdp/numbat/tree/master/numbat/modules

closes: vim/vim#17643

20eb68a8f2

Co-authored-by: 0xadk <0xadk@users.noreply.github.com>

test/old/testdir/test_filetype.vim

@@ -564,6 +564,7 @@ func s:GetFilenameChecks() abort
     \ 'nsis': ['file.nsi', 'file.nsh'],
     \ 'ntriples': ['file.nt'],
     \ 'nu': ['file.nu'],
+    \ 'numbat': ['file.nbt'],
     \ 'obj': ['file.obj'],
     \ 'objdump': ['file.objdump', 'file.cppobjdump'],
     \ 'obse': ['file.obl', 'file.obse', 'file.oblivion', 'file.obscript'],