not all extensions linked from extensions manual page

[elelay]

We need to go through all extension docs and ensure they are referenced on https://gpodder.github.io/docs/extensions#default-extensions-included-with-gpodder (docs/extensions.md)

[thp]

It would be cool if there was a script that generated the part here, since this is chore that will come up later:

https://github.com/gpodder/gpodder.github.io/blob/master/docs/extensions.md#default-extensions-included-with-gpodder

And then generate a file (same basename as the extension) for each extension:

https://github.com/gpodder/gpodder.github.io/tree/master/docs/extensions

Would probably need a way to also auto-generate the metadata in each file, i.e. the title, list of configuration options, link to extension source.

For urlwatch, I just have a --features command-line option in the tool that outputs the data, and for now I manually copy it over into the docs, but it is really something that's best automated (not the documentation writing, but the list of extensions and their config options, something that can be mechanically derived from the source code):

https://github.com/thp/urlwatch/blob/0425631dc379a4ac1b4ef56ca5c76b5bbde4c067/docs/source/filters.rst?plain=1#L91-L92