Refactor Mongoose documentation

PUBLISHED_FROM=e9a4e5c7b4a1d03b93a2a79e29de19e60e919929

docs/c-api/resolv.h/mg_resolve_async.md

@@ -0,0 +1,11 @@
+---
+title: "mg_resolve_async()"
+decl_name: "mg_resolve_async"
+symbol_kind: "func"
+signature: |
+  int mg_resolve_async(struct mg_mgr *mgr, const char *name, int query,
+                       mg_resolve_callback_t cb, void *data);
+---
+
+See `mg_resolve_async_opt()` 
+