Repo Checks: Enable Github Actions Auto Updating on All Repos

[feanil]

Like we did here: https://github.com/openedx/.github/blob/master/.github/dependabot.yml

More details: # https://docs.github.com/en/code-security/supply-chain-security/keeping-your-dependencies-updated-automatically/keeping-your-actions-up-to-date-with-dependabot

[farhan]

Relevant code references:
https://github.com/openedx/repo-tools/blob/master/edx_repo_tools/dependabot_yml.py
https://github.com/openedx/.github/blob/master/.github/workflows/bulk_repo_update.yml

[feanil]

@salman2013 using the existing tool sounds great, I think we want to add the dependabot.yml but we don't need to add a reviewer for now.