Add utility function to compute/check ZIM descriptions

[benoit74]

Fix #110

Changes:

• new utility function compute_descriptions in inputs.py to compute ZIM-compliant descriptions based on default and user-provided values
• small improvements to tox configuration
• small type hint fix of handle_user_provided_file in inputs.py

[codecov]

Codecov Report

Patch coverage: 100.00% and no project coverage change.

Comparison is base (4f8c3cc) 100.00% compared to head (591c6dc) 100.00%.

Additional details and impacted files

@@            Coverage Diff            @@
##              main      #111   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files           32        32           
  Lines         1302      1319   +17     
=========================================
+ Hits          1302      1319   +17     

Files Changed	Coverage Δ
src/zimscraperlib/constants.py	100.00% <100.00%> (ø)
src/zimscraperlib/inputs.py	100.00% <100.00%> (ø)
src/zimscraperlib/zim/metadata.py	100.00% <100.00%> (ø)

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[rgaudin]

Works as expected ; thank you but this new Descriptions class is uncalled for. We don't want to extend the API surface which such a thing. I believe returning a tuple here is appropriate.

[rgaudin]

@benoit74 I had this stashed. Can you review this commit?
Also please add your change to CHANGELOG and we'll be good to merge

[benoit74]

It's ok for me, and I've added my CHANGELOG.
I let you merge since I can't 😆