Update pkgdown actions based on branch reorganization

[brookslogan]

Goal is to have separate main & dev documentation sites, with different styling, like cmu-delphi/epidatr. Plus some miscellaneous small updates thrown in. [Before, we only would run pkgdown checks on PRs to dev, not render&update the actual site on pushes to dev, since it would clobber the main version of the site.]

[nmdefries]

The DESCRIPTION file on dev needs a 4-component version number (x.x.x.x) to trigger the dev-site behavior. Without this, the dev site will keep overwriting the main public version. The main version needs to be a 3-component number (x.x.x). Some more info and links in this PR.

4-component versions complicates automated version bumping, if that's set up in this repo. That will need to be addressed in any workflow files, or noted in any instructions for manual releases.

Recommend including info somewhere about how this works on the public site and how to generate local previews. This is the text I included for developers of epidatr.

[dshemetov]

This seems like a good PR to bump our package version to dev release. Could you change the version to 0.7.0.9000?

[dshemetov]

Ah I see the version bump happened in #377

[dshemetov]

should be good to go after #385

[brookslogan]

Thanks @dshemetov for addressing the issues. Are we still missing release process documentation as mentioned by @nmdefries? If so, should we put that in another Issue or handle it here?

[dshemetov]

Fine to handle it here.

• Merge Djm/pkgdown prettier #379
• Add Nat's dev site docs documentation.