Feature 1731 docs

[j-opatz]

Pull Request Testing

• Describe testing already performed for these changes:
  This branch was already merged, but additional documentation updates (tc_pairs, grid-diag) were added since the merge.

• Recommend testing for the reviewer(s) to perform, including the location of input datasets, and any additional instructions:
  Quick language, spelling check should suffice.

• Do these changes include sufficient documentation updates, ensuring that no errors or warnings exist in the build of the documentation? [Yes or No]
  These are only documentation updates

• Do these changes include sufficient testing updates? [Yes or No]

• Will this PR result in changes to the test suite? [Yes or No]
  No
  If yes, describe the new output and/or changes to the existing output:
  

• Please complete this pull request review by [Fill in date].
  5/10, the major release

Pull Request Checklist

See the METplus Workflow for details.

• Complete the PR definition above.
• Ensure the PR title matches the feature or bugfix branch name.
• Define the PR metadata, as permissions allow.
  Select: Reviewer(s), Project(s), and Milestone
• After submitting the PR, select Linked Issues with the original issue number.
• After the PR is approved, merge your changes. If permissions do not allow this, request that the reviewer do the merge.
• Close the linked issue and delete your feature or bugfix branch from GitHub.

[JohnHalleyGotway]

Please see suggestions for minor edits.

[j-opatz]

Comment changes have been approved

[JohnHalleyGotway]

Looks great, thanks John. I approve.