Add infodesk matrix channel

docs/facilities.md

@@ -2,7 +2,7 @@
 
 ## Infodesk
 
-If you have a question about the camp, e.g. where to find what, our job is
+If you have a question about the camp, e.g., where to find what, our job is
 to know, or to find out. Follow us on Mastodon or join our Matrix Channel for
 Announcements!
 
@@ -10,7 +10,7 @@ Announcements!
 
 * Infodesk Tent: [At O 13](https://map.events.ccc.de/camp/2023/map/#17.48/53.030177/13.305944/G,M,O) at the main way leading straight away from the entrance after 250m.
 * DECT: 1111 (Dial-In-Number: TBD)
-* Matrix: TBD
+* Matrix: [#camp2023-infodesk:events.ccc.de](https://matrix.to/#/#camp2023-infodesk:events.ccc.de)
 * IRC: #c3infodesk on hackint.org
 * Mastodon: [@c3infodesk@chaos.social](https://chaos.social/@c3infodesk) (requests via the other channels are preferred).