`static-lang-word-lists` testing: ensure script & language are recognised by HarfBuzz

Pull in `harfrust` as a dev dependency and smash all the word lists' metadata through:

- `Tag::from_str` + `Script::from_iso15924_tag` for script
- `Language::from_str` for language

See the `impl WordListExt for WordList` code in Font Height to see how things are checked there

We won't be able to remove that validation from Font Height as we may eventually add runtime-defined word lists which don't necessarily need to have HarfBuzz recognised scripts/languages (and pulling in `harfrust` as a runtime dependency to be able to check that feels very big & overkill)

This should be implementable as an integration test (and therefore without codegen 🙌)