test: Add missing peer dependency

@ngtools/webpack requires a peer dependency of enhanced-resolve@^3.1.0. It currently relies on webpack providing this dependency and on NPM 3+ flat tree installation. Webpack could remove this dependency or NPM change the tree structure. This change also removes a NPM warning about missing peer dependency.

Author: aecz

packages/@angular/cli/package.json

@@ -41,6 +41,7 @@
     "diff": "^3.1.0",
     "ember-cli-normalize-entity-name": "^1.0.0",
     "ember-cli-string-utils": "^1.0.0",
+    "enhanced-resolve": "^3.1.0",
     "exports-loader": "^0.6.3",
     "extract-text-webpack-plugin": "3.0.0",
     "file-loader": "^0.10.0",