Merge pull request #11 from ben/dependabot/github_actions/actions/che…

…ckout-3

Bump actions/checkout from 2 to 3

Merge pull request progit#1667 from progit/ben/github-actions

Set up GitHub actions for CI and release builds

Merge pull request progit#89 from schacon/appendix-final

Appendix Final

Merge remote-tracking branch 'origin/master' into appendix

Conflicts:
	book/10-git-internals/sections/refs.asc

Merge pull request progit#43 from schacon/chapter-3-polish

Chapter 3 polish

add atlas.json and cover image