Drop support for Python 3.6

[hugovk]

New version of #46 now #49 released.

cycle	latest	release	eol
3.10	3.10.0	2021-10-04	2026-10-04
3.9	3.9.9	2020-10-05	2025-10-05
3.8	3.8.12	2019-10-14	2024-10-14
3.7	3.7.12	2018-06-27	2023-06-27
3.6	3.6.15	2016-12-23	2021-12-23

[codecov]

Codecov Report

Merging #50 (d479bee) into main (e7291f2) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main      #50   +/-   ##
=======================================
  Coverage   56.52%   56.52%           
=======================================
  Files           4        4           
  Lines         552      552           
=======================================
  Hits          312      312           
  Misses        240      240           

Flag	Coverage Δ
GHA_Ubuntu	56.52% <ø> (ø)
GHA_macOS	56.52% <ø> (ø)

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