Increase test coverage, correct type hints

[mochipon]

• Hopefully increase test coverage.
• Support Python 3.6.
• Utilize pre-commit more
• Utilize mypy for static typing: fixed a lot of mistakes and omissions.

[codecov]

Codecov Report

Merging #29 (4a8b03e) into main (7bf62a7) will increase coverage by 1.95%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main      #29      +/-   ##
==========================================
+ Coverage   93.88%   95.83%   +1.95%     
==========================================
  Files           8        8              
  Lines         376      384       +8     
==========================================
+ Hits          353      368      +15     
+ Misses         23       16       -7     

Impacted Files	Coverage Δ
pysesame3/auth.py	94.23% <100.00%> (+1.92%)	⬆️
pysesame3/cloud.py	100.00% <100.00%> (ø)
pysesame3/device.py	100.00% <100.00%> (ø)
pysesame3/helper.py	100.00% <100.00%> (ø)
pysesame3/history.py	100.00% <100.00%> (ø)
pysesame3/lock.py	84.33% <100.00%> (+6.95%)	⬆️

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