title: How to open a file upon button click PySimpleGui
body: <p>my goal is to create a button and when the button is pressed to open txt file.</p>
  <p>I have already created button in the layout but I can't figure out how to make a txt file open upon button click.</p>
  <p>This is python and I'm using PySimpleGui as framework.</p>
  <p>The txt file is very long(~600k lines) so ideally it will be in another popup</p>
  <p>Couldn't find anything in the documentation nor the cookbook</p>