Drop Python 3.6 support

[hukkin]

TODO:

• add changelog

[codecov-commenter]

Codecov Report

Merging #134 (8b804d3) into master (96dfe2c) will not change coverage.
The diff coverage is 100.00%.

❗ Current head 8b804d3 differs from pull request most recent head f44cee3. Consider uploading reports for the commit f44cee3 to get more accurate results

@@            Coverage Diff            @@
##            master      #134   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files            3         3           
  Lines          495       497    +2     
  Branches        93        93           
=========================================
+ Hits           495       497    +2     

Impacted Files	Coverage Δ
tomli/_parser.py	100.00% <100.00%> (ø)
tomli/_re.py	100.00% <100.00%> (ø)
tomli/__init__.py	100.00% <0.00%> (ø)

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