Fix: display episode images from RSS item tags in HTML UI

[elalemanyo]

Fixes a bug where episode images were not shown in the web UI.
The parser now checks common item-level image locations (namespaced itunes:image, media:thumbnail / media:content, and plain image), and falls back to channel-level images when necessary.

Changes:

• Use querySelector with namespace escapes for itunes:image.
• Add checks for media:thumbnail / media:content and plain image elements.
• Add basic favicon
• Remove some spaces 🙈

[mxpv]

@chkuendig PTAL

[chkuendig]

Sorry for the delay. This indeed seems to be an issue with some browsers I think. Changing from querySelector to getElementsByTagName is the correct way of doing things.

I don't see any checks for media:thumbnail and media:content though? Maybe i missed them, generally this would be much easier to review if the 4 changes were their own commit, especially the whitespace/formatting change.