Build docs from GitHub Actions, fix lint errors, and add logo to docs

[MaxGhenis]

No description provided.

[codecov]

Codecov Report

Merging #104 into master will decrease coverage by 0.21%.
The diff coverage is 79.87%.

@@            Coverage Diff             @@
##           master     #104      +/-   ##
==========================================
- Coverage   82.20%   81.98%   -0.22%     
==========================================
  Files          27       27              
  Lines         545      544       -1     
==========================================
- Hits          448      446       -2     
- Misses         97       98       +1     

Impacted Files	Coverage Δ
microdf/_optional.py	100.00% <ø> (ø)
microdf/income_measures.py	71.42% <0.00%> (-6.35%)	⬇️
microdf/inequality.py	51.11% <0.00%> (ø)
microdf/tests/test_inequality.py	100.00% <ø> (ø)
microdf/tests/test_quantile_chg.py	100.00% <ø> (ø)
microdf/agg.py	26.66% <28.57%> (-4.59%)	⬇️
microdf/ubi.py	20.00% <33.33%> (-8.58%)	⬇️
microdf/tests/test_compare.py	68.00% <50.00%> (ø)
microdf/taxcalc.py	75.55% <53.84%> (+1.64%)	⬆️
microdf/custom_taxes.py	46.42% <55.55%> (ø)
... and 16 more

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 95c37de...8f0a11f. Read the comment docs.

[MaxGhenis]

I'm not sure how to handle remaining I100 and I201 flake8 errors, filed PyCQA/flake8-import-order#174 for the I201s.