Fix mongoose docs generation

PUBLISHED_FROM=331821dcd1f7dc8a94581cd8a9b51aa00a89fddc

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

@@ -0,0 +1,12 @@
+---
+title: "mg_send_websocket_framev()"
+decl_name: "mg_send_websocket_framev"
+symbol_kind: "func"
+signature: |
+  void mg_send_websocket_framev(struct mg_connection *nc, int op_and_flags,
+                                const struct mg_str *strings, int num_strings);
+---
+
+Like `mg_send_websocket_frame()`, but composes a single frame from multiple
+buffers. 
+