title: How can I add an icon to the Gmail side-bar?
body: <p>What method do I use in a Google-apps script for Gmail to add an icon to the side-panel?</p>
  
  <p>I can't seem to find any reference to it in the docs. Thanks.</p>
  
  <p><img src="https://images.squarespace-cdn.com/content/v1/560b4d0ce4b0edef1f1760e9/1551192247798-QC1ZDZ4SISE68EL9E93Y/ke17ZwdGBToddI8pDm48kJ4di5aBTiZ_hSazkNcehONZw-zPPgdn4jUwVcJE1ZvWQUxwkmyExglNqGp0IvTJZamWLI2zvYWH8K3-s_4yszcp2ryTI0HqTOaaUohrI8PI-fZNGQHDQDTCxJe-4YhCVGnor1chbK6d9KuwySdnhrI/Gmail-Apps-Sidepanel-Screenshot1.png?format=2500w" alt="This bit"></p>