chore(deps): update dependency typescript to ~2.9.0 (#190)

Author: renovate[bot]

package-lock.json

@@ -73,7 +73,7 @@
     "nyc": "^12.0.2",
     "source-map-support": "^0.5.5",
     "tmp": "0.0.33",
-    "typescript": "~2.8.3"
+    "typescript": "~2.9.0"
   },
   "peerDependencies": {
     "typescript": "^2.7.1"