Ruby: support HAML template files

It would be nice if CodeQL supported extraction of [HAML](https://github.com/haml/haml) template files into the database, like it does for ERB template files. One challenge here is that there is no existing tree-sitter grammar for HAML yet, unlike for ERB template files, making it more difficult to integrate with the extractor. Tree-sitter grammar support for HAML has also come up elsewhere: https://github.com/zed-industries/extensions/issues/179