Update dependency rollup-plugin-typescript2 to v0.20.0

Author: renovate-bot

package.json

@@ -17,7 +17,7 @@
     "babel-plugin-inferno": "5.0.1",
     "rollup": "0.57.1",
     "rollup-plugin-babel": "3.0.3",
-    "rollup-plugin-typescript2": "0.12.0",
+    "rollup-plugin-typescript2": "0.20.0",
     "typescript": "2.8.1"
   },
   "dependencies": {