Add a Doxyfile and preliminary module-level docs.

src/ssb.js.h

@@ -1,6 +1,14 @@
 #pragma once
 
+/**
+** \defgroup ssb_js SSB Interface
+** Exposes SSB to JS.
+** @{
+*/
+
 typedef struct JSContext JSContext;
 typedef struct _tf_ssb_t tf_ssb_t;
 
 void tf_ssb_register(JSContext* context, tf_ssb_t* ssb);
+
+/** @} */