h-feed support

[pcarrier]

• [x] I have read this document: https://miniflux.app/opinionated.html#feature-request

https://microformats.org/wiki/h-feed is used by a bunch of indieweb resources, like https://stream.indieweb.org/

It'd be great to support it natively in miniflux.

In the meantime, one can convert through https://granary.io/