Switch template to Copier

[ypid]

See https://copier.readthedocs.io/en/stable/

This will allow to do the:

• search for "com_myorg_rules_mylang" and replace with the name you'll use for your workspace
• search for "myorg" and replace with GitHub org
• search for "mylang", "Mylang", "MYLANG" and replace with the language/tool your rules are for
• rename directory "mylang" similarly

steps for the automatically user after asking for those details.

Also, when this template involves, users can use Copier to pull in those changes to their instantiated projects. Ref: https://copier.readthedocs.io/en/stable/updating/