feature: support PlanetScale

[tsirysndr]

PlanetScale is a serverless MySQL platform : https://planetscale.com/ I saw in the shuttle docs that we already have a plugin to provision databases on AWS RDS https://docs.shuttle.rs/resources/shuttle-aws-rds The idea is to create also a plugin to provision databases on PlanetScale like what we have for AWS RDS

[chesedo]

@tsirysndr can you provide some info and links as to what PlanetScale is? A minimal hello world example would also be great