chore(package): update @angular-devkit/build-ng-packagr to version 0.901.6

Closes #241

Author: greenkeeper[bot]

package.json

@@ -57,7 +57,7 @@
   "dependencies": {},
   "devDependencies": {
     "@angular-devkit/build-angular": "~0.803.19",
-    "@angular-devkit/build-ng-packagr": "~0.803.19",
+    "@angular-devkit/build-ng-packagr": "~0.901.6",
     "@angular/cli": "^8.3.19",
     "@angular/common": "8.2.14",
     "@angular/compiler": "8.2.14",