improve karax documentation

readme.rst

@@ -2,8 +2,8 @@ Karax – Single page applications in Nim |travis|
 ================================================
 
 Karax is a framework for developing single page applications in Nim.
-It's still in heavy development, so keep in mind that the API is subject
+The API is reasonably stable and version 1 should arrive anytime soon
-to change.
+now.
 
 To try it out, run::
 
@@ -184,6 +184,27 @@ Once you have tasted this power there is no going back and languages
 without AST based macro system simply don't cut it anymore.
 
 
+Attaching data to an event handler
+==================================
+
+Since the type of an event handler is ``(ev: Event; n: VNode)`` or ``()`` any
+additional data that should be passed to the event handler needs to be
+done via Nim's closures. In general this means a pattern like this:
+
+.. code-block:: nim
+
+  proc menuAction(menuEntry: kstring): proc() =
+    result = proc() =
+      echo "clicked ", menuEntry
+
+  proc buildMenu(menu: seq[kstring]): VNode =
+    result = buildHtml(tdiv):
+      for m in menu:
+        nav(class="navbar is-primary"):
+          tdiv(class="navbar-brand"):
+            a(class="navbar-item", onclick = menuAction(m)):
+
+
 DOM diffing
 ===========