Add latest release notes to index (#1728)

Forgot to add the new release notes to the index, so they can show up in
the website. Update the release date. Minor corrections to RST syntax.

Add release notes for v0.24.0 (#1655)

Add release notes for SimPEG v0.24.0, and update the version switcher.

Fix date in release notes (#1574)

Fix release date for v0.23.0.

Add release notes for v0.22.2 (#1532)

Add release notes for v0.22.2. Add v0.22.2 to `versions.json`.

Add latest merged PR to release notes for v0.22.1 (#1510)

Add #1509 to the release notes for v0.22.1.

Add release notes for v0.22.0 (#1499)

Add release notes for v0.22.0. Add new version to `versions.json` file
and mark it as the latest.

Add release notes for v0.21.1 (#1416)

Add release notes for patch `v0.21.1`.

Publish documentation on azure (#1412)

Adds a publish step on the documentation test CI so we can download it and
view it.

Merge pull request #1282 from mplough-kobold/main

Refresh links in documentation

Merge pull request #1275 from jcapriot/0.20.0_staging

0.20.0 staging