OPDS1 images for root navigation feed are not preserved when converted to OPDS2, and Thorium doesn't display them anyway

[danielweck]

The data image URL encoding seems to be supported at the OPDS1 parser level but they are not preserved in OPDS2 in the navigation feed:

https://www.ebooksgratuits.com/opds/
https://streamer.edrlab.org/opds-v1-v2-convert/https%3A%2F%2Fwww.ebooksgratuits.com%2Fopds%2F

Thorium 2.4.1 and 3.0.0-alpha.1 both show no cover images, but that's because they do not exist in the feed (they only exist at the root navigation, which we only display textually, without images):

https://www.ebooksgratuits.com/opds/feed.php?mode=genre&id=2

https://www.ebooksgratuits.com/opds/
https://streamer.edrlab.org/opds-v1-v2-convert/https%3A%2F%2Fwww.ebooksgratuits.com%2Fopds%2Ffeed.php%3Fmode%3Dgenre%26id%3D2