Manually call loop

[woubuc]

Right now this library expects the user to call app.wait_for_message() which causes the app to loop indefinitely, locking the thread until the app exits.

However, I want to run some custom logic in my app loop and then update the tray icon based on that logic (change the icon & update some menu items). Is it possible to just call the update function from my own loop, rather than have this library run the loop for me?

[rafamerlin]

I'm trying to do the same, maybe you can use the code from this PR as it seems to do the job.
#43