Support for database URLs

[mikerockett]

My app is being deployed to Fly.io, which uses DATABASE_URL for connections. Whilst one could easily populate the applicable environment variables, like DB_HOST, it would be nice to see this package support DATABASE_URL, which Laravel supports out of the box (in which case the laravel-db-snapshots package would need to be updated to support this).

[freekmurze]

If the code is simple, I'd accept a PR that adds this. Make sure to update docs and tests.

[mikerockett]

I’ve opened #196 for your review. Tests were failing, all passing now.