Picture downloading while "Retrieve content from the browse"

Hi there,
First of all, thanks for this option it's a lot helpfull for bypassing mass media sites with authorization and sites that were blocked in a country.
However, I've just tried the option and unfortunately **couldn't upload images through the extension**. It would be nice to upload them into wallabag server as well as the article text.

Start by tracing the extension's “Retrieve content from the browse” option and how it handles article text versus images. No files or tests are named in the issue, so identify the upload path and reproduce the missing image behavior against a wallabag server. Done means images are uploaded with the article content and the flow is covered by appropriate verification.

Written by the indexing model from the issue text.