proxify http request in article when jarr is served in https

[jaesivsm]

When articles contain images served in http and jarr is served in https, the browser will block the content.

The easiest solution is to proxify access to those images.

[jaesivsm]

Ok, I wrote this completely misunderstanding how mixed-content are handled. Visibly, mixed-content is tolerated through <img src=[...]> but not <img srcset=[...]>. So the simple fix is to remove the srcset when it can't be displayed (jarr is served over https and src is set so the image will still be valid).