doc updates

[mathause]

• Closes go over docs #286
• Fully documented, including whats-new.rst

[codecov-commenter]

Codecov Report

Merging #313 (4ff0bbe) into master (7d7c7f1) will not change coverage.
The diff coverage is n/a.

❗ Current head 4ff0bbe differs from pull request most recent head c12752e. Consider uploading reports for the commit c12752e to get more accurate results

@@           Coverage Diff           @@
##           master     #313   +/-   ##
=======================================
  Coverage   98.74%   98.74%           
=======================================
  Files          15       15           
  Lines        1193     1193           
=======================================
  Hits         1178     1178           
  Misses         15       15           

Flag	Coverage Δ
bare-minimum	91.79% <ø> (ø)
min-all-deps	97.84% <ø> (ø)
unittests	98.74% <ø> (ø)

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[mathause]

TODO: fix notebooks

• notebooks/method.ipynb
• notebooks/mask_2D.ipynb
• notebooks/mask_3D.rst

natural_earth deprecation and shading

[mathause]

Add

sphinx:
  fail_on_warning: true

to readthedocs.yml