Add support for Python 3.10

[s-t-e-v-e-n-k]

Now that Python 3.10 has been released, we should test it in CI.

[codecov-commenter]

Codecov Report

Merging #2073 (5bc6af1) into master (b10dbe3) will increase coverage by 0.00%.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #2073   +/-   ##
=======================================
  Coverage   98.86%   98.86%           
=======================================
  Files         108      108           
  Lines       11064    11065    +1     
=======================================
+ Hits        10938    10939    +1     
  Misses        126      126           

Impacted Files	Coverage Δ
github/GithubObject.py	98.82% <0.00%> (+<0.01%)	⬆️

---

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 b10dbe3...5bc6af1. Read the comment docs.