title: PySimpleGUI get selected text
body: <p>New to PySimpleGUI.</p>
  
  <p>I have a multiline input box :</p>
  
  <pre><code>    layout1 = [[sg.Multiline(size=(45,5),key='-IN-')],...
      window1 = sg.Window('Source',layout1,finalize=True)
      event1,values1 = window1.read()
  </code></pre>
  
  <p>I type in some text and then using the mouse, I highlight a portion of the text. How do I get that selected (highlighted) text?</p>
  
  <p>In Tkinter, I simply used :</p>
  
  <pre><code>        self.title = self.e.selection_get() 
  </code></pre>
  
  <p>but I like what I've seen of PySimpleGUI and would to try to stick with it.</p>
  
  <p>I have searched here, github and google and haven't found anything about this. Hoping it is something simple and that someone is able to point me in the right direction.</p>
  
  <p>Thanks,</p>
  
  <p>Randy</p>