Keeping people in the loop about new version of CodiMD is not easy. When
people don't keep an eye on GitHub it's easy to miss new versions.

To help people keeping their software up to date, this patch adds hints
to check out our community channel or simply the GitHub Atom feed
generated for based on the release page to get informed about new
versions.

Signed-off-by: Sheogorath <sheogorath@shivering-isles.com>