Add a Doxyfile and preliminary module-level docs.

src/httpd.js.h

@@ -1,5 +1,18 @@
 #pragma once
 
+/**
+** \defgroup httpd_js HTTPD Interface
+** Exposes the \ref http server to script and registers a number of built-in
+** endpoints.
+**
+** core/core.js is gradually being moved from JS to C here, at which point this will
+** no longer be a bridge between the two and instead primarily expose the web API.
+**
+** @{
+*/
+
 #include "quickjs.h"
 
 void tf_httpd_register(JSContext* context);
+
+/** @} */