fix(@ngtools/webpack): support typescript 2.8 + 2.9

Author: mattlewis92

packages/ngtools/webpack/package.json

@@ -31,7 +31,7 @@
     "webpack-sources": "^1.1.0"
   },
   "peerDependencies": {
-    "typescript": "~2.4.0 || ~2.5.0 || ~2.6.0 || ~2.7.0",
+    "typescript": "~2.4.0 || ~2.5.0 || ~2.6.0 || ~2.7.0 || ~2.8.0 || ~2.9.0",
     "webpack": "^4.0.0"
   }
 }