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 #329 (c9ddca6) into master (89c4d8c) will increase coverage by 0.02%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #329      +/-   ##
==========================================
+ Coverage   82.46%   82.48%   +0.02%     
==========================================
  Files          11       11              
  Lines         650      651       +1     
==========================================
+ Hits          536      537       +1     
  Misses        114      114              

Impacted Files	Coverage Δ
vcspull/config.py	96.69% <0.00%> (+0.02%)	⬆️

---

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 89c4d8c...c9ddca6. Read the comment docs.