title: When you use this plugin you must install `typescript`. error
body: <p>I am using yarn 2 and react with webpack.</p>
  <p>In my package is <code>&quot;typescript&quot;: ...</code> defined. Once I start <code>yarn start</code> I am getting an error:</p>
  <pre><code>yarn workspace test start
  When you use this plugin you must install `typescript`.
  </code></pre>
  <p>What is wrong? How should I fix it? Or debug it?</p>