Update readme, fix pyproject and add more tests

[goanpeca]

No description provided.

[codecov]

Codecov Report

Attention: Patch coverage is 81.81818% with 2 lines in your changes missing coverage. Please review.

Project coverage is 75.97%. Comparing base (35fdc18) to head (a2ee3a2).

Files with missing lines	Patch %	Lines
napari_update_checker/qt_update_checker.py	66.66%	1 Missing ⚠️
napari_update_checker/utils.py	50.00%	1 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##             main       #5       +/-   ##
===========================================
+ Coverage   44.76%   75.97%   +31.21%     
===========================================
  Files           3        4        +1     
  Lines         172      179        +7     
===========================================
+ Hits           77      136       +59     
+ Misses         95       43       -52     

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