Add embedded web chat client (closes #7) (#8)

schema/commands/NICK.json

@@ -0,0 +1,22 @@
+{
+  "$schema": "https://json-schema.org/draft/2020-12/schema",
+  "$id": "https://git.eeqj.de/sneak/chat/schema/commands/NICK.json",
+  "title": "NICK",
+  "description": "Change nickname. C2S: request new nick. S2C: notification of nick change. RFC 1459 §4.1.2.",
+  "$ref": "../message.json",
+  "properties": {
+    "command": { "const": "NICK" },
+    "from": { "type": "string", "description": "Old nick (S2C)." },
+    "body": {
+      "type": "array",
+      "items": { "type": "string" },
+      "description": "New nick (single-element array).",
+      "minItems": 1,
+      "maxItems": 1
+    }
+  },
+  "required": ["command", "body"],
+  "examples": [
+    { "command": "NICK", "from": "oldnick", "body": ["newnick"] }
+  ]
+}