vim-patch:9.1.0424: filetype: slint files are not recognized

Problem:  filetype: slint files are not recognized
Solution: Detect '*.slint' files as slint filetype,
          include basic sling filetype plugin
          (Riley Bruins)

closes: vim/vim#14808

aa3104b07a

Co-authored-by: Riley Bruins <ribru17@hotmail.com>

runtime/ftplugin/slint.vim

@@ -0,0 +1,15 @@
+" Vim filetype plugin
+" Language:	slint
+" Maintainer:	Riley Bruins <ribru17@gmail.com>
+" Last Change:	2024 May 19
+
+if exists('b:did_ftplugin')
+  finish
+endif
+let b:did_ftplugin = 1
+
+" Set 'comments' to format dashed lists in comments.
+" Also include ///, used for Doxygen.
+setl comments=sO:*\ -,mO:*\ \ ,exO:*/,s1:/*,mb:*,ex:*/,:///,:// commentstring=//\ %s
+
+let b:undo_ftplugin = 'setl com< cms<'

runtime/lua/vim/filetype.lua

@@ -970,6 +970,7 @@ local extension = {
   cdf = 'skill',
   sl = 'slang',
   ice = 'slice',
+  slint = 'slint',
   score = 'slrnsc',
   sol = 'solidity',
   smali = 'smali',

test/old/testdir/test_filetype.vim

@@ -655,6 +655,7 @@ func s:GetFilenameChecks() abort
     \ 'slang': ['file.sl'],
     \ 'sage': ['file.sage'],
     \ 'slice': ['file.ice'],
+    \ 'slint': ['file.slint'],
     \ 'slpconf': ['/etc/slp.conf', 'any/etc/slp.conf'],
     \ 'slpreg': ['/etc/slp.reg', 'any/etc/slp.reg'],
     \ 'slpspi': ['/etc/slp.spi', 'any/etc/slp.spi'],