Support default value for toggle embeddings

Change-Id: I2216bf73528deef0dc4d73f8cb5948655477e4a8
diff --git a/dev/js/src/plugin/server.js b/dev/js/src/plugin/server.js
index 669708c..1fa0002 100644
--- a/dev/js/src/plugin/server.js
+++ b/dev/js/src/plugin/server.js
@@ -233,6 +233,10 @@
 
           let state = stateClass.create([true, false]);
 
+          if (onClick["default"] !== undefined) {
+            state.setIfNotYet(onClick["default"]);
+          };
+
           // TODO:
           //   Lazy registration (see above!)
           KorAP.Panel[panel].actions().addToggle(title, {'cls':["title"]}, state);