Fix mongoose docs generation

PUBLISHED_FROM=331821dcd1f7dc8a94581cd8a9b51aa00a89fddc

docs/c-api/mg_net.h/mg_vprintf.md

@@ -0,0 +1,10 @@
+---
+title: "mg_vprintf()"
+decl_name: "mg_vprintf"
+symbol_kind: "func"
+signature: |
+  int mg_vprintf(struct mg_connection *, const char *fmt, va_list ap);
+---
+
+Same as `mg_printf()`, but takes `va_list ap` as an argument. 
+