add url check.

Readme.md

@@ -162,7 +162,25 @@ curl -v -X POST \
 | salt          | BLOB     | NOT NULL                            |     |
 | created_at    | INTEGER  | NOT NULL                            |     |
 
+## WebRTC Signal 服务
 
+```javascript
+// /api/v1/webrtc/signal/{id}
+{
+    "id": "server",
+    "type": "request"
+}
+{
+    "id": "DDeFJqNHPN",
+    "type": "offer",
+    "sdp": "v=0\r\no=rtc 2294191555 0 IN IP4 127.0.0.1\r\ns=-\r\nt=0 0\r\n ......"
+}
+{
+    "id": "server",
+    "type": "answer",
+    "sdp": "v=0\r\no=- 7471496884559213660 2 IN IP4 127.0.0.1\r\ns=-\r\nt=0 0\r\n ......"
+}
+```
 
 ## Live2D 模型添加