Bugfix/upcoming readthedocs deprecation fixes

[scrasmussen]

TYPE: bug fix, enhancement

KEYWORDS: documentation, readthedocs, MkDocs

SOURCE: Soren Rasmussen, NCAR

DESCRIPTION OF CHANGES:

• meets upcoming readthedocs deprecations
  • readthedocs requirement for a version 2 .readthedocs.yaml file.
  • Uses build.os instead of build.image in .readthedocs.yaml
• better organization and fixes to MkDocs yaml. Note, it will probably look differently after being merged but built locally it looked like the following:

• Changing readthedocs link to 'latest', which points to the main branch, since that is where the current fixes are being committed. It was pointing to the develop branch's 'develop' url.
• A few documentation formatting changes and link additions
• Google analytics method has changed, commenting out for now

TESTS CONDUCTED: built locally

Checklist

• Closes issue #xxxx (An issue must exist or be created to be closed. The
  issue describes and documents the problem and general solution, the PR
  describes the technical details of the solution.)
• Tests added (unit tests and/or regression/integration tests)
• Backwards compatible
• Requires new files? If so, how to generate them.
• Fully documented