Documentation: Need explicit WACCM-X documentation

What's the issue?

📚 Please describe the problem you’ve noticed in the documentation.

The docs have a section for how to use WACCM with DART, but there is no specific documentation for WACCM-X. This leads to some misleading/incorrect info if you are trying to use this documentation for WACCM-X, as the DART docs are primarily referencing WACCM.

For example, the correct compset for WACCM-X is FXHIST, but the documentation only mentions the compset for WACCM ( FWHIST)

Where did you find the issue?

Provide the location(s) of the issue:

• File name or URL: https://docs.dart.ucar.edu/en/latest/models/cam-fv/readme.html#waccm
• Section name or header: waccm

Suggestions for improvement

If you have any ideas to fix or generally improve this documentation, please share them.

Create a documentation section for WACCM-X in addition to the existing WACCM section

Anything else we should know?

Include any other relevant details, such as references, screenshots, or related discussions.

Nick Pedatella has offered to write some documentation to address this; this is planned to be added in the next few weeks.

Start at docs.dart.ucar.edu/en/latest/models/cam-fv/readme.html#waccm and read the existing WACCM section. Add a separate WACCM-X section that distinguishes the FXHIST compset from WACCM’s FWHIST guidance. Done means the documentation clearly and explicitly covers WACCM-X without misleading users.