Quieten binder-badge bot

[manics]

Use an action to comment once and update the comment instead of repeatedly commenting.

See #2 (comment)
This action should ensure there's only one comment that gets updated.

[github-actions]

👈 Launch a binder notebook on this branch for commit 32bc0e7

[consideRatio]

For this to work in the JupyterHub GitHub org, I believe you need to be explicit about the permissions granted to the github token. By default, you only have read inside our org.

Docs about this: https://docs.github.com/en/actions/reference/authentication-in-a-workflow#permissions-for-the-github_token

I think you need...

jobs:
  badge:
    permissions:
      pull-requests: write

Perhaps also contents: read? I'm not sure.

[consideRatio]

Ping @manics, I've not used your action before but we can absolutely go for it! You will need to update permissions though.

[github-actions]

👈 Launch a binder notebook on this branch for commit 89345d3