Node.js 20

[keunes]

Hello,

Thanks for making this action available!

Running it, I'm getting the following warning in GitHub:
Node.js 16 actions are deprecated. Please update the following actions to use Node.js 20: actions/checkout@v2, actions-ecosystem/action-add-labels@v1. For more information see: https://github.blog/changelog/2023-09-22-github-actions-transitioning-from-node-16-to-node-20/.

The referenced blog post contains the following:

Modify your actions to run on Node 20 instead of Node 16. For guidance, refer to the Actions configuration settings.

[revelt]

related to existing #459