title: ESLint complaining about empty constructor and ngOnInit-implementation
body: <p>In my Angular application, the rule <a href="https://github.com/typescript-eslint/typescript-eslint/blob/master/packages/eslint-plugin/docs/rules/no-empty-function.md" rel="noreferrer"><em>no-empty-function</em></a>, triggered an error for my constructor. Well, it <strong>is indeed</strong> an empty body there but the constructor itself needs to be there, because I inject a service.</p>
  <pre><code>export class ClientListComponent implements OnInit {
    constructor(service: AuxService) { }
    ngOnInit() { }
    ...
  }
  </code></pre>
  <p>Interestingly, it also complains about the implemented method for the interface. However, the error messages vary between those two, which perplexes me additionally.</p>
  <blockquote>
  <p>Unexpected empty constructor.<br />
  Unexpected empty method 'ngOnInit'.</p>
  </blockquote>
  <p>So, it clearly distinguishes between a plain method (be that still required one due to the implemented interface, which itself is wrong in my opinion to nag about) and a constructor. I'm sure that the creators have heard about dependency injection, so I can't understand what I'm missing.</p>