Enable automerge for Renovate Bot (#16)

Author: daniel-shuy

renovate.json

@@ -4,5 +4,16 @@
   ],
   "ignoreDeps": [
     "org.scalatest:scalatest"
-  ]
+  ],
+  "rebaseStalePrs": true,
+  "automerge": true,
+  "major": {
+    "automerge": false
+  },
+  "packageRules": [{
+    "packageNames": [
+      "org.scalameta:sbt-scalafmt"
+    ],
+    "automerge": false
+  }]
 }