chore(ng13): install required peerDependencies

Author: christopherthielen

package.json

@@ -67,6 +67,7 @@
     "jest": "26.6.3",
     "jest-preset-angular": "8.4.0",
     "ng-packagr": "^12.0.0",
+    "postcss": "^8.0.0",
     "prettier": "^2.0.5",
     "pretty-quick": "^3.1.0",
     "rxjs": "^6.5.4",
@@ -75,7 +76,7 @@
     "tslint": "^6.1.0",
     "typescript": "~4.3.5",
     "utf-8-validate": "5.0.4",
-    "zone.js": "0.10.3"
+    "zone.js": "0.11.4"
   },
   "ngPackage": {
     "lib": {