Add crosslinks and minor edits to docs

[gspetro-NOAA]

Description

• This PR adds crosslinks and minor edits to docs. This way, you won't need to update image numbers each time you add or remove images. RTD will do it automatically.
  It also adds an empty references.bib file to eliminate a build warning about contrib-bibtex. (You can remove that file and the bibtex_bibfiles line in conf.py that references it, but you'll also have to remove contrib-bibtex from the list of extensions in that case.)

Type of change

• Bug fix (fixes something broken)
• New feature (adds functionality)
• Maintenance (code refactor, clean-up, new CI test, etc.)

Change characteristics

• Is this a breaking change (a change in existing functionality)? NO
• Does this change require a documentation update? YES
• Does this change require an update to any of the following submodules? NO

How has this been tested?

I built the docs locally and on ReadTheDocs. You can view the docs for my fork here (with functioning crosslinks): https://gsp-gwc.readthedocs.io/en/docs4csps/noaa_csp.html

Checklist

• Any dependent changes have been merged and published
• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have documented my code, including function, input, and output descriptions
• My changes generate no new warnings
• New and existing tests pass with my changes
• This change is covered by an existing CI test or a new one has been added
• Any new scripts have been added to the .github/CODEOWNERS file with owners
• I have made corresponding changes to the system documentation if necessary