Always resize too big images

[benoit74]

Fix #90

Changes:

• always resize images using more pixels than HD (1280*720 pixels) so that conversion to webp and optimization does not consumes too much memory ; side-effect : limit final ZIM size
  • 1280*720 pixels has been chosen as a viable default because it still allows pretty neat pictures even when viewed full screen on most devices (we have some big photos sometimes in libretexts.org) ... but we will probably need to check this in the wild
• fix some un-needed code 🤦🏻‍♂️

[codecov]

Codecov Report

Attention: Patch coverage is 33.33333% with 6 lines in your changes missing coverage. Please review.

Project coverage is 49.27%. Comparing base (31b0fcb) to head (cf87e36).
Report is 4 commits behind head on main.

Files with missing lines	Patch %	Lines
scraper/src/mindtouch2zim/asset.py	25.00%	6 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #109      +/-   ##
==========================================
+ Coverage   49.23%   49.27%   +0.04%     
==========================================
  Files          20       20              
  Lines        1170     1175       +5     
  Branches      164      165       +1     
==========================================
+ Hits          576      579       +3     
- Misses        583      585       +2     
  Partials       11       11              

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[rgaudin]

LGTM ; see simplification suggestion

[rgaudin]

Can you rename PR?