CI, package updates, 3.10 support, 3.6 deprecation, add precommit

[tony]

• poetry 1.1.7 -> 1.1.12, use new installer
• Drop python 3.6
• Add python 3.10
• CI: test 3.7 and 3.10 (low and high end of supported releases)
• Update myst-parser and sphinx-autodoc-typehints
• Add .pre-commit-config.yaml
• black: update 21.9b0 -> 21.12b0

[codecov]

Codecov Report

Merging #317 (10bf38b) into master (6a9764e) will increase coverage by 0.02%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #317      +/-   ##
==========================================
+ Coverage   89.38%   89.41%   +0.02%     
==========================================
  Files          16       16              
  Lines         424      425       +1     
==========================================
+ Hits          379      380       +1     
  Misses         45       45              

Impacted Files	Coverage Δ
cihai/conversion.py	87.50% <0.00%> (+0.14%)	⬆️

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