Use user timeout in multithreading polling

PUBLISHED_FROM=dbf75bfba087f1b0aa0531e5003ba3e69ed1a6ab

docs/c-api/net.h/intro.md

@@ -30,6 +30,7 @@ items:
   - { name: struct_mg_add_sock_opts.md }
   - { name: struct_mg_bind_opts.md }
   - { name: struct_mg_connect_opts.md }
+  - { name: struct_mg_multithreading_opts.md }
 ---
 
 NOTE: Mongoose manager is single threaded. It does not protect

docs/c-api/net.h/struct_mg_multithreading_opts.md

@@ -0,0 +1,12 @@
+---
+title: "struct mg_multithreading_opts"
+decl_name: "struct mg_multithreading_opts"
+symbol_kind: "struct"
+signature: |
+  struct mg_multithreading_opts {
+    int poll_timeout; /* Polling interval */
+  };
+---
+
+Optional parameters for mg_enable_multithreading_opt() 
+