Fix mongoose docs generation

PUBLISHED_FROM=331821dcd1f7dc8a94581cd8a9b51aa00a89fddc

docs/c-api/mg_http.h/struct_websocket_message.md

@@ -0,0 +1,14 @@
+---
+title: "struct websocket_message"
+decl_name: "struct websocket_message"
+symbol_kind: "struct"
+signature: |
+  struct websocket_message {
+    unsigned char *data;
+    size_t size;
+    unsigned char flags;
+  };
+---
+
+WebSocket message 
+