Refactor Mongoose documentation

PUBLISHED_FROM=e9a4e5c7b4a1d03b93a2a79e29de19e60e919929

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

@@ -0,0 +1,17 @@
+---
+title: "struct mg_resolve_async_opts"
+decl_name: "struct mg_resolve_async_opts"
+symbol_kind: "struct"
+signature: |
+  struct mg_resolve_async_opts {
+    const char *nameserver_url;
+    int max_retries;    /* defaults to 2 if zero */
+    int timeout;        /* in seconds; defaults to 5 if zero */
+    int accept_literal; /* pseudo-resolve literal ipv4 and ipv6 addrs */
+    int only_literal;   /* only resolves literal addrs; sync cb invocation */
+    struct mg_connection **dns_conn; /* return DNS connection */
+  };
+---
+
+Options for `mg_resolve_async_opt`. 
+