Allow using pscale connect with the serverless driver for JavaScript

[jacobwgillespie]

Hey! We've been using pscale connect --execute 'pnpm dev' in local development, to connect to our database. We've recently been using the @planetscale/database serverless driver and would love to be able to use that with pscale connect as well.

Currently the injected DATABASE_URL environment variable assumes the MySQL protocol - I'm not sure what would be involved in offering that same functionality but for the serverless driver, I could imagine a --protocol http option or similar flag to switch proxy modes.

[magnusmay]

This would be a much needed feature and awesome!

[mscoutermarsh]

We're tracking this in the database.js repo here: #621

Thanks!