Provide a default Jupyter Releaser GitHub App

[jtpio]

Problem

Currently creating a custom GitHub App and managing its secrets adds friction for adopting the releaser. One also has to store the secrets somewhere and make sure they are correctly added to the release environment on GitHub.

Proposed Solution

Could it be possible to develop an "official" releaser GitHub app in https://github.com/jupyter-server, that other orgs or users could install directly?

That app would required the needed permissions to perform the necessary actions on the repo (push access, create github releases...).

Additional context

This could ease the releaser setup in cases where one would like to use the releaser for a repo, but does not have access to the org settings directly for creating the app. Instead a "GitHub app installation request" would be sent to the org admin, which could be easier to accept than creating a new app.

[jtpio]

For Jupyter orgs, it would be similar to installing the Meeseek app for doing backports: https://github.com/apps/lumberbot-app