chore: add Greenkeeper config file

Author: greenkeeper[bot]

greenkeeper.json

@@ -0,0 +1,12 @@
+{
+  "groups": {
+    "default": {
+      "packages": [
+        "package.json",
+        "samples/sample-datavault-react/package.json",
+        "samples/sample-datavault-solidity/package.json",
+        "templates/template-solidity/package.json"
+      ]
+    }
+  }
+}