As an active part of the community prefers Matrix.org over Gitter, we
should link Matrix.org as a place to meet us.

As the matrix and gitter channels are interconnected. We don't loose any
message if a person decides to go for one or another.

We use an more universal way of translation to make it easier to provide
a link to various platforms.

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