feat: add toolbox contract shell and testkit

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

@@ -0,0 +1,32 @@
+{
+  "$schema": "https://git.add-ideas.de/zemion/toolbox-sdk/raw/branch/main/schemas/toolbox-app.v1.schema.json",
+  "schemaVersion": 1,
+  "id": "de.add-ideas.example-tool",
+  "name": "Example Tool",
+  "version": "0.1.0",
+  "description": "A minimal toolbox-compatible React application.",
+  "entry": "./",
+  "icon": "./icon.svg",
+  "categories": ["examples"],
+  "tags": ["react", "toolbox"],
+  "integration": {
+    "contextVersion": 1,
+    "launchModes": ["navigate", "new-tab"],
+    "embedding": "unsupported"
+  },
+  "requirements": {
+    "secureContext": false,
+    "workers": false,
+    "indexedDb": false,
+    "crossOriginIsolated": false
+  },
+  "privacy": {
+    "processing": "local",
+    "fileUploads": false,
+    "telemetry": false
+  },
+  "source": {
+    "repository": "https://git.add-ideas.de/zemion/toolbox-sdk",
+    "license": "Apache-2.0"
+  }
+}