chore: add highlighting for codeowners files

Add `CODEOWNERS` as an additional file type for `git-ignore` in the
language file. `CODEOWNERS`'s grammar is close enough to that of
`.gitignore`, this can be used to avoid making a new grammar
specifically for `CODEOWNERS` files.

Resolves: helix-editor#8091

languages.toml

@@ -1380,7 +1380,7 @@ source = { git = "https://github.com/mtoohey31/tree-sitter-gitattributes", rev =
 name = "git-ignore"
 scope = "source.gitignore"
 roots = []
-file-types = [".gitignore", ".gitignore_global", ".ignore", ".prettierignore", ".eslintignore", ".npmignore"]
+file-types = [".gitignore", ".gitignore_global", ".ignore", ".prettierignore", ".eslintignore", ".npmignore", "CODEOWNERS"]
 injection-regex = "git-ignore"
 comment-token = "#"
 grammar = "gitignore"