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 #344 (0f287a3) into master (fccac42) will increase coverage by 0.04%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #344      +/-   ##
==========================================
+ Coverage   87.06%   87.10%   +0.04%     
==========================================
  Files          16       16              
  Lines        1515     1520       +5     
==========================================
+ Hits         1319     1324       +5     
  Misses        196      196              

Impacted Files	Coverage Δ
setup.py	0.00% <ø> (ø)
tests/test_common.py	98.26% <0.00%> (-1.74%)	⬇️
tests/test_tmuxobject.py	100.00% <0.00%> (ø)
libtmux/test.py	42.85% <0.00%> (+0.21%)	⬆️
tests/conftest.py	85.10% <0.00%> (+0.32%)	⬆️
libtmux/common.py	86.93% <0.00%> (+0.50%)	⬆️
libtmux/session.py	81.54% <0.00%> (+0.59%)	⬆️
libtmux/window.py	84.33% <0.00%> (+0.60%)	⬆️

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