feat: bump angular min supported version to v20

Author: damingerdai

packages/angular-toaster/package.json

@@ -28,8 +28,8 @@
     "growl"
   ],
   "peerDependencies": {
-    "@angular/common": "^18.0.0",
-    "@angular/core": "^18.0.0",
+    "@angular/common": "^20.0.0",
+    "@angular/core": "^20.0.0",
     "rxjs": "^7.4.0"
   },
   "dependencies": {