Add note about Universe WiFi

Author: martinwoodward

src/content/hacks/badge-custom-username.mdx

@@ -21,6 +21,9 @@ The badge app refuses to fetch data until `GITHUB_USERNAME` and Wi-Fi credential
 - Wi-Fi SSID and password for a 2.4 GHz network
 - Your GitHub username (case-sensitive)
 
+Note that at the Universe event, there is a WiFi access point
+that you can connect to in the "Hack The Badge" area.
+
 ## Steps
 
 1. **Enter USB storage mode** (double-tap `Reset`).