Fix mongoose docs generation

PUBLISHED_FROM=331821dcd1f7dc8a94581cd8a9b51aa00a89fddc

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

@@ -0,0 +1,12 @@
+---
+title: "Client API reference"
+symbol_kind: "intro"
+decl_name: "mg_http_client.h"
+items:
+  - { name: mg_connect_http.md }
+  - { name: mg_connect_http_opt.md }
+  - { name: mg_http_create_digest_auth_header.md }
+---
+
+
+