More specific follow up of #13 and #328

FreshRSS already supports quite well News+ (https://github.com/noinnion/newsplus ).

It was also tested against a modified version of https://github.com/ericmann/gReader-Library

It is currently being tested (alpha beta quality) against a fork of EasyRSS (https://play.google.com/store/apps/details?id=com.pursuer.reader.easyrss).

To improve compatibility, it would be nice to check with additional clients.

See how to get started with the API