add form to create employee

Reviewed-on: #18
Reviewed-by: Get in my car i have candy <huydw@proton.me>

src/app/services/employee-api.service.ts

@@ -19,4 +19,8 @@ export default class EmployeeApiService {
   public getAll(): Observable<Employee[]> {
     return this.http.get<Employee[]>(`${EmployeeApiService.BASE_URL}/employees`)
   }
+
+  public create(employee: Employee) {
+    return this.http.post<Employee>(`${EmployeeApiService.BASE_URL}/employees`, employee)
+  }
 }