Add releasinator config file

[subsidel]

📺 What

In preparation for a change to the release automation, adds a config file for the bot "releasinator" (previously tvr-buildatron)

🛠 How

Copy existing release behaviour over into a config file in the root directory.

✅ Testing

After this change is merged, and the change to the release automation happens (likely Fri 28th March):

• If the changes are successful a "test" release will be created and should not have any particular differences other than the name/image of the bot making the release.