Put memory consumption under control

[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 44.26%. Comparing base (d802fef) to head (e0b8b01).

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

Additional details and impacted files

@@                 Coverage Diff                 @@
##           ui_enhancements     #109      +/-   ##
===================================================
+ Coverage            44.19%   44.26%   +0.06%     
===================================================
  Files                   20       20              
  Lines                 1163     1168       +5     
  Branches               168      169       +1     
===================================================
+ Hits                   514      517       +3     
- Misses                 637      639       +2     
  Partials                12       12              

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[rgaudin]

LGTM ; see simplification suggestion

[rgaudin]

Why using this? There are resize options that keep aspect ratio and you just pass the largest one (so the other one fits)

[rgaudin]

Can you rename PR?