Test on python 3.10

[dionhaefner]

Fixes #251

[codecov]

Codecov Report

Merging #252 (967a1ed) into main (ce7958b) will not change coverage.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##             main     #252   +/-   ##
=======================================
  Coverage   98.13%   98.13%           
=======================================
  Files          45       45           
  Lines        2254     2254           
  Branches      329      329           
=======================================
  Hits         2212     2212           
  Misses         24       24           
  Partials       18       18           

Impacted Files	Coverage Δ
terracotta/handlers/singleband.py	100.00% <100.00%> (ø)

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[dionhaefner]

Failing tests will be fixed by #240.