Add rss-listing and link in help page

[pedro-psb]

This adds @himdel rss feed link into pulp website and a simple listing of it's content.

Its added to the end of the help page (after quicklinks).

[pedro-psb]

I tried creating an html page /rss/index.html with <link rel="alternate" type="application/rss+xml" title="Changes RSS Feed" href="https://himdel.eu/feed/pulp-changes.json" /> in the head tag, but the rss client I tried wasnt able to fetch from that link (only directly from your server).

But I guess it's okay to keep your server link, if you don't mind.
Later I can create a similar script in python to generate the rss-json on build time (it's built/published nightly).