Support Python 3.11

[hugovk]

Python 3.11 beta is out on Friday with full release in October:

• 3.11.0 beta 1: Friday, 2022-05-06
• 3.11.0 final: Monday, 2022-10-03

https://peps.python.org/pep-0664/

Changes proposed in this pull request:

• Test 3.11-dev on GitHub Actions
• Add py311 to tox.ini
• Add Trove classifier
• Update some config

[codecov]

Codecov Report

Merging #181 (283ac03) into master (56baf04) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #181   +/-   ##
=======================================
  Coverage   94.03%   94.03%           
=======================================
  Files           5        5           
  Lines        2245     2245           
=======================================
  Hits         2111     2111           
  Misses        134      134           

Flag	Coverage Δ
GHA_Ubuntu	?
GHA_Windows	?
GHA_macOS	?
macos-latest	94.03% <ø> (?)
ubuntu-latest	94.03% <ø> (?)
windows-latest	93.89% <ø> (?)

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