Add Docker Compose stack and Pi notes

LiveKit on host networking so WebRTC can advertise a reachable address,
plus the server and website.

infra/pi/pistation.json.example

@@ -0,0 +1,5 @@
+{
+  "serverUrl": "http://pistation.local:8080",
+  "enrollmentToken": "paste-the-token-from-the-admin-panel",
+  "joinUrl": "pistation.local:3000"
+}