Support for a DATABASE_URL style config

[mattrobenolt]

I think either providing a helper such as configFromEnv('DATABASE_URL') or something along these lines to parse a config in a traditional mysql://user:pass@host would be nice for configuration, we can even be a bit more planetscale specific with our URI such as pscale://user:pass@aws.connect.psdb.cloud. I don't personally have an opinion if this is it's own thing like:

connect(configFromEnv())

Or built into the config such as:

connect({uri: env['DATABASE_URL']})

Up to whatever you think is most common or would be most desirable to adopt.

This would allow simplifying an application config with one variable instead of 3 different ones, and we can leverage the already standard DATABASE_URL that's established.

[steven-tey]

Potentially related: planetscale/f1-championship-stats#18