Translation of Git episode 2

[rikutakei]

Translation of Git episode 2.

I had a minor merge conflict when pulling from the swcarpentry-ja/i18n ja branch, so something might be a bit "off".

よろしくおねがいします:slightly_smiling_face:

[joelnitta]

Thanks for the translation! I just have a few comments/suggestions.

[masamiy]

Great work! My comments are really only suggestions.

[rikutakei]

I have added everyone's suggestions, so I think this should be good for merging

[TomKellyGenetics]

Great job Riku, let's see if we can trigger GitHub Actions: https://github.com/swcarpentry-ja/i18n/actions?query=workflow%3ARender-Webpages

[TomKellyGenetics]

Had to mess with the script and formatting but now it's builds webpages automatically when a commit is pushed to ja branch. This includes PRs after they're merged.

Page updated by bot:
https://swcarpentry-ja.github.io/git-novice/ja/_episodes/02-setup/index.html

GitHub Actions instance (runs 3 lessons simultaneously).
https://github.com/swcarpentry-ja/i18n/actions/runs/357290157

Long story on how to give it permissions and make it run in an empty docker container should work like magic from now on.