feat: support parsing regex literals

[tommy]

This doesn't yet add support for doing anything wiht them – the evaluator still panics when it reaches one.

thread 'main' panicked at src/evaluator.rs:135:18:
not implemented: TODO: node kind not yet supported: Regex(
    RegexLiteral(
        Regex(
            "[0-9]",
        ),
    ),
)

Note: we should probably switch from regex to https://docs.rs/regress/latest/regress/ , which targets the javascript regex syntax, which I assume JSONata uses (or at least is closer to).

[aesterline]

Nice! LGTM