Hi there,
while searching for FreshRSS extensions I stumbled upon this repository, but couldn't find any other resource.
I would suggest to have a place where users can link their own extensions.
This is not only a shameless try to drop a link to my freshrss youtube extension ;-) but I believe that the FreshRSS community would benefit from it.

The easiest way for the start could be to include a new section in this repositories README with links to "third party extensions". I could sent in a PR if you like the idea.

Any other suggestions?