Added my ssh key, and added a bit of contact info to the Matrix documentation.
Reviewed-on: Fediversity/Fediversity#172
Reviewed-by: kiara Grouwstra <kiara@procolix.eu>
Co-authored-by: Hans van Zijst <hans@procolix.com>
Co-committed-by: Hans van Zijst <hans@procolix.com>
