Add key navigation to docs

[prisae]

Summary

This PR enables moving forward/backward in the docs with the right/left arrow keys on the keyboard. I quite enjoy this feature in documentations that have enabled it.

If you want to see how it works, test it over at, e.g., https://empymod.emsig.xyz.

PR Checklist

• Just a docs-configuration change, the PR checklist does mostly not apply.

@simpeg/simpeg-developers - ready for review.

[prisae]

Oh. I realized that the default was True, but it changed recently:
pydata/pydata-sphinx-theme#1100

So it apparently is against the "gold standard" of keyboard navigation. Too bad, I love it.

Anyway, I leave it for a short while open, curious to see what you think.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 85.57%. Comparing base (55cfbfa) to head (abcfb76).
Report is 2 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1668      +/-   ##
==========================================
- Coverage   86.19%   85.57%   -0.62%     
==========================================
  Files         420      405      -15     
  Lines       54931    53499    -1432     
  Branches     5124     5088      -36     
==========================================
- Hits        47350    45784    -1566     
- Misses       6163     6320     +157     
+ Partials     1418     1395      -23     

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[santisoler]

😮 I didn't know about this feature. Let's merge it!