adding shared service

src/app/shared/shared-service.service.spec.ts

+import { TestBed } from '@angular/core/testing';
+
+import { SharedServiceService } from './shared-service.service';
+
+describe('SharedServiceService', () => {
+  let service: SharedServiceService;
+
+  beforeEach(() => {
+    TestBed.configureTestingModule({});
+    service = TestBed.inject(SharedServiceService);
+  });
+
+  it('should be created', () => {
+    expect(service).toBeTruthy();
+  });
+});

src/app/shared/shared-service.service.ts

+import { Injectable } from '@angular/core';
+import { Subject } from 'rxjs';
+
+@Injectable({
+  providedIn: 'root'
+})
+export class SharedService {
+  private numberSource = new Subject<number>();
+  number$ = this.numberSource.asObservable();
+
+  setNumber(number: number) {
+    this.numberSource.next(number);
+  }
+}