Add size change to GitHub Check summary

[USSRLivesOn]

Currently, the GitHub Check just displays whether or not the action itself ran successfully:

It would be nice to have a more informative summary, perhaps including the change in size, like done in https://github.com/siddharthkp/bundlesize#build-status-for-github:

I know a lot of the logic already exists for the comment version of the action, and it would be great if it could be ported to the GitHub Checks version as well.

[developit]

Yes! I 100% want this, been meaning to find some time to implement it.

[swissspidy]

See also https://github.blog/2022-05-09-supercharging-github-actions-with-job-summaries/