chore(package): update @angular-devkit/schematics to version 8.3.20

Closes #49

Author: greenkeeper[bot]

package.json

@@ -47,7 +47,7 @@
     "moment": "^2.23.0"
   },
   "devDependencies": {
-    "@angular-devkit/schematics": "^7.3.7",
+    "@angular-devkit/schematics": "^8.3.20",
     "@angular/compiler": "^7.2.11",
     "@angular/compiler-cli": "^7.2.11",
     "@angular/platform-browser-dynamic": "^7.2.11",