Doc improvements

[d-chambers]

Description

This PR:

• Adds examples for some top-level DASCore functions
• Improves the site styling by tweaking the css
• Makes example patch functions public
• Adds a function for getting a dataframe of functions, their cross links, and descriptions.

Checklist

I have (if applicable):

• referenced the GitHub issue this PR closes.
• documented the new feature with docstrings or appropriate doc page.
• included a test. See testing guidelines.
• your name has been added to the contributors page (docs/contributors.md).
• added the "ready_for_review" tag once the PR is ready to be reviewed.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (9ade640) 99.51% compared to head (75f6528) 99.52%.
Report is 1 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #335      +/-   ##
==========================================
+ Coverage   99.51%   99.52%   +0.01%     
==========================================
  Files          92       91       -1     
  Lines        7170     7191      +21     
==========================================
+ Hits         7135     7157      +22     
+ Misses         35       34       -1     

Flag	Coverage Δ
unittests	99.52% <100.00%> (+0.01%)	⬆️

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