fix: allow angular 8 peer dependency

Author: mattlewis92

package.json

@@ -90,7 +90,7 @@
     "zone.js": "^0.8.26"
   },
   "peerDependencies": {
-    "@angular/core": ">=6.0.0 <8.0.0"
+    "@angular/core": ">=6.0.0 <9.0.0"
   },
   "config": {
     "commitizen": {