Autolabel PRs with the name of new / modified addons

[sbidoul]

Got this idea after a conversation with @sebastienbeau

Is your feature request related to a problem?

In OCA it is not easy to get an overview of the PRs that impact addons you are interested in.

Describe the solution you'd like

The bot already has logic to know which modules are added/updated by a PR.
When a PR is created or when new commits are pushed to a PR the bot could look at modified addons and label the PR with {type}: {addon_name}. Where type would describe what happens (such as addon new, addon upd, addon mig).