Can't use pgloader to migrate sqlite + Feature request: Migrate from sqlite to postgresql

# Use case

What problem you are trying to solve?
Migrate from sqlite to postgresql

Note alternatives you considered and why they are not useful.

# Your idea for a solution

How your solution would work in general? Maybe just a script to help
Note that some overly complicated solutions may be rejected because maddy is
meant to be simple.

- [x] I'm willing to help with the implementation