Improve error message for sleeping databases

[penberg]

If a database (or actually the group) is sleeping, you get the following error message:

$ turso db create foo
Error: could not create database foo: cannot create database on group default because it is sleeping

Let's add information on how to wake it up. For example, with an URL to documentation.

[rodrigozrusso]

The same applies to other commands, e.g:

turso db shell [database] < ./migration.sql
⣾  Connecting to database
Error: failed to execute SQL:
error code 502:

It could display an error message indicating that the database (or group) is sleeping and add a link to wake it up.