add ".h" extension to the C file-types

Previously, if you changed the tab-width for C but did not add ".h" to C file types, headers used Cpp's indentation (default is 2), which is undesirable.

languages.toml

@@ -380,7 +380,7 @@ source = { git = "https://github.com/Joakker/tree-sitter-json5", rev = "c23f7a9b
 name = "c"
 scope = "source.c"
 injection-regex = "c"
-file-types = ["c"] # TODO: ["h"]
+file-types = ["c", "h"]
 comment-token = "//"
 language-servers = [ "clangd" ]
 indent = { tab-width = 2, unit = "  " }