fix(service-worker): add missing rxjs peer dependency (#59747)

The `@angular/service-worker` package now explicitly declares `rxjs` as a peer dependency.

PR Close #59747

Author: alan-agius4

packages/service-worker/package.json

@@ -22,7 +22,8 @@
     "tslib": "^2.3.0"
   },
   "peerDependencies": {
-    "@angular/core": "0.0.0-PLACEHOLDER"
+    "@angular/core": "0.0.0-PLACEHOLDER",
+    "rxjs": "^6.5.3 || ^7.4.0"
   },
   "repository": {
     "type": "git",