title: Change res.getHeader() to res.get()
body: <p>I have the following code</p>
  
  <pre><code>const compress = require('compression');
  
  export const handleCompression = compress({
    filter: function (req: express.Request, res: express.Response) {
      return (/json|text|javascript|css|font|svg/).test(res.getHeader('Content-Type'));
    },
    level: 9
  });
  </code></pre>
  
  <p>I get this warning from TypeScript:</p>
  
  <p><a href="https://i.stack.imgur.com/cipR5.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/cipR5.png" alt="enter image description here"></a></p>
  
  <p>Would it be correct to change the call to:</p>
  
  <pre><code>res.get('Content-Type')
  </code></pre>
  
  <p>?</p>