Handling not supported engines

[jaggernoth]

Is it ok to create PR's for unsupported dialects? As long as it doesn't break existing logic of course.
One I've got in mind is Presto's UNNEST : https://prestodb.io/docs/current/sql/select.html#unnest
Having unnest in the 'FROM' section currently generates extra tables from tokens inside UNNEST and t
I can work around it in my code, but it would be much nicer to have it handled in the library itself.

[collerek]

I guess it's welcomed, that's how all backend support started😁

If that won't break the functionality or introduce significant complication ( of already complicated) of parsing than we would be more than happy 😊