MariaDB 11 support

[tomcoonen]

Since MariaDB 11 differentiates more from MySQL, and to still support v10 I've split them up.
While upgrading an app you might need to switch back, and removing the MariaDB volume is extra work. By naming the volumes differently you have no issues there.

[taylorotwell]

So how would the maria11.stub actually get into the user's docker-compose.yml file?

[tomcoonen]

@taylorotwell If you're ok with the approach, I can add the rest of the code?
Not sure if we should keep 'mariadb' or change it to 'mariadb10'?

[taylorotwell]

It could potentially be kept separate from Maria 10.

[tomcoonen]

@taylorotwell Made the rest of the changes, tried to keep as much as possible in line with what is already there.

[driesvints]

@tomcoonen don't forget to mark the PR back to ready if you need a review 😉

[Jubeki]

In the docker-compose.yaml (the stubs in this case), I would also use mariadb instead of mariadb10/mariadb11 because this is also the host which will configured in the .env

Your normally also only have on database. We also only use the name mysql for MySQL 8 and not mysql8.