Added sphinx copybutton

[georgemccabe]

Also updated the documentation GitHub Actions workflow to install python packages using the docs/requirements.txt file so the list of packages there and on ReadTheDocs are in sync.

Pull Request Testing

• [X] Describe testing already performed for these changes:
  

Viewed the documentation on ReadTheDocs

• [X] Recommend testing for the reviewer(s) to perform, including the location of input datasets, and any additional instructions:
  

Confirm that the format of the copy button is acceptable. https://i-wrf.readthedocs.io/en/feature_copybutton/Users_Guide/matthewjetstream.html

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

• [X] Do these changes include sufficient testing updates? [Yes]

• [X] Will this PR result in changes to the test suite? [N/A]
  If yes, describe the new output and/or changes to the existing output:
  

• [X] Please complete this pull request review by 5/30/2024.
  

Pull Request Checklist

• [X] Review the source issue metadata (required labels, projects, and milestone).
• [X] Complete the PR definition above.
• [X] Ensure the PR title matches the feature or bugfix branch name.
• [X] Define the PR metadata, as permissions allow. Select: Reviewer(s) Select: Organization level software support Project or Repository level development cycle Project Select: Milestone as the version that will include these changes
• [X] After submitting the PR, select Development issue 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.

[Trumbore]

The buttons look and work great. Thanks, George!