[RSS] ability to show `media:thumbnail` instead of url preview

[farfromrefug]

I would like the rss feed to show the media thumbnail if any. The idea is that i use a photo rss to share photos directly in riot group. However right now it shows only the url preview of the website. Is that doable? I see that it could be configurable seeing the last commits.

BTW can i write a custom bot for my self hosted riot im instance (synapse). I could then test it and push a PR here. Also how is this released? Is it part of Synapse? I mean if i want to use your latest changes for RSS how would i proceed?

Thanks