Add network icon ISUPPORT token

Closes: ircv3/ircv3-ideas#123

Author: emersion

extensions/network-icon.md

@@ -0,0 +1,28 @@
+---
+title: "Network Icon"
+layout: spec
+work-in-progress: true
+copyrights:
+  -
+    name: "Simon Ser"
+    period: "2025"
+    email: "contact@emersion.fr"
+---
+
+## Notes for implementing work-in-progress version
+
+This is a work-in-progress specification.
+
+## Description
+
+The `NETWORK` ISUPPORT token allows servers to advertise their network name. This specification adds a new ISUPPORT token to advertise a network icon.
+
+## The `draft/ICON` ISUPPORT token
+
+If a server publishes a `draft/ICON` ISUPPORT token, the value MUST be a URL to an image. The URL SHOULD use the "https" scheme.
+
+Servers MAY implement [extended-isupport](extended-isupport.html) to allow clients to fetch the network icon before connection registration.
+
+## Example
+
+    S: :irc.example.org 005 * NETWORK=Example draft/ICON=https://example.org/icon.svg :are supported by this server