resolved page flickering - wait for page to fully load

[JaimeFRF]

Closes #172

• Set a timeout probably does not always work depending on how good your connection is
• Tried to enforce waiting for all the previous work to be done before displaying the page. Didn't solve the problem; which probably meant that with the timeout, we were giving time to the page itself to finish loading something
• Now , explicitly saying : if the page is done loading show it ; if not addEventListener when "load" fires (the page is finished loading) now you can show it

[toni-santos]

that's it! quite simple and should work everytime, good job 👍

[thePeras]

✅ 🛫