title: How can I check if package is installed in the project
body: <p>I'm creating a module that looks for a text field in scene.
  if TextMeshPro is installed it looks for it, and if not, look for regular textfield/text mesh</p>
  
  <p>the question is: how can I condition (pseudo code)</p>
  
  <pre><code>if(textMeshProExists)
      Look for A
  else
      Look for B
  </code></pre>