[CI] Update logos/ dir if necessary

This will fix the following:

Thanks! I think it would be nice to update the logos folder itself. I think the file sizes are all going to be small enough that it'll be ok to do so.

It does not update PR branches to avoid permission issues but instead commits to main if necessary after a PR has been merged.

Example run:

The commit that was added after a PR added an org: https://github.com/SaschaMann/JuliaOrgLogos/commits/main
The corresponding release: https://github.com/SaschaMann/JuliaOrgLogos/releases/tag/release-2020-11-21T130315Z

ViralBShah / JuliaOrgLogos

[CI] Update logos/ dir if necessary #8