vim-patch:9.1.0460: filetype: lintstagedrc files are not recognized

Problem:  filetype: lintstagedrc files are not recognized
Solution: recognize '.lintstagedrc' files as json filetype
          (İlyas Akın)

see: https://github.com/lint-staged/lint-staged

closes: vim/vim#14897

7577afd5ef

Co-authored-by: İlyas Akın <ilyas.akin@kuika.com>

runtime/lua/vim/filetype.lua

@@ -1451,6 +1451,7 @@ local filename = {
   ['.firebaserc'] = 'json',
   ['.prettierrc'] = 'json',
   ['.stylelintrc'] = 'json',
+  ['.lintstagedrc'] = 'json',
   ['flake.lock'] = 'json',
   ['.babelrc'] = 'jsonc',
   ['.eslintrc'] = 'jsonc',