Keep GitHub Actions up to date with GitHub's Dependabot

[cclauss]

• https://docs.github.com/en/code-security/dependabot/working-with-dependabot/keeping-your-actions-up-to-date-with-dependabot
• https://docs.github.com/en/code-security/dependabot/dependabot-version-updates/configuration-options-for-the-dependabot.yml-file#package-ecosystem

[niccokunzmann]

Thanks! That is nice... I did not know that one could do that :)

[niccokunzmann]

Hm. Usually, we record these changes in this file:
https://github.com/collective/icalendar/blob/master/CHANGES.rst

Would you be willing to delete the file and mention the content there, so it is recorded in the changelog?

Thanks again for the PR!

[cclauss]

Generated:
#592