Rename `master` branch to `main`

[chalin]

Related: google/docsy#765

• Rename master branch to main
• Set github_branch to main in the config file. Eventually, once we've updated beyond 0.6.0, we can comment out the option since main will be the default - Set version to 0.7.0-dev, adjust default branch, and more #213
• Set Production branch to main via https://app.netlify.com/sites/goldydocs/settings/deploys

---

GitHub's advice

git branch -m master main
git fetch origin
git branch -u origin/main main
git remote set-head origin -a

Adapt these instructions, depending on the name of your remote, etc.

[LisaFC]

Given that we've updated the main Docsy site, we should probably do this one as well ASAP. @chalin did you make the update on Docsy and will it be simple enough to do it again here?

[chalin]

I'd be glad to do it here. Do you want this done before or after Hugo-module support lands?

[LisaFC]

Maybe let's merge the module support and then we can do it in a separate PR as we'll need to update the config.toml in the modules PR.

[chalin]

Done!