feat: add toolbox contract shell and testkit

examples/react-app/public/toolbox.catalog.json

@@ -0,0 +1,23 @@
+{
+  "$schema": "https://git.add-ideas.de/zemion/toolbox-sdk/raw/branch/main/schemas/toolbox-catalog.v1.schema.json",
+  "schemaVersion": 1,
+  "id": "de.add-ideas.example-toolbox",
+  "name": "Example Toolbox",
+  "home": "./",
+  "theme": {
+    "mode": "system",
+    "brand": "Example Toolbox"
+  },
+  "apps": [
+    {
+      "manifest": "./toolbox-app.json",
+      "enabled": true
+    },
+    {
+      "name": "ADD Ideas",
+      "entry": "https://add-ideas.de/",
+      "launch": "new-tab",
+      "enabled": true
+    }
+  ]
+}