Added support for customizing ZIM logo

[josephlewis42]

Fixes #32

This change adds a new flag --logo-format that can be used to set a logo for the ZIM from a URL or local file. It supports formatting directives. This means we can fetch files from freeCodeCamp/devdocs which does have 32x32 images (labeled as 16@2x.png in the repo). I didn't make this the default because they look fine but not great, but the property might still be useful with an S3 bucket or mounted volume.

devdocs2zim --output /tmp/devdocs \
  --slug=http,lua~5.4,vue~3 \
  --logo-format="https://raw.githubusercontent.com/freeCodeCamp/devdocs/refs/heads/main/public/icons/docs/{slug_without_version}/16@2x.png"

I made the method that fetches and resizes the image static so I think it could be lifted up into devdocs2zim.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 92.28%. Comparing base (9604fb8) to head (7b219f5).
Report is 2 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #37      +/-   ##
==========================================
+ Coverage   91.85%   92.28%   +0.43%     
==========================================
  Files           4        4              
  Lines         356      376      +20     
  Branches       45       48       +3     
==========================================
+ Hits          327      347      +20     
  Misses         25       25              
  Partials        4        4              

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[benoit74]

Thank you, few comments

[benoit74]

LGTM