Hi. I just checked on my own Chrome installation: It is working as intended. Very strange that your firefox installation also doesn't work. I would check the following:
1. You're launching the HTML by double-clicking on it from the unzipped folder
2. You've checked your browsers settings: (Firefox) https://support.mozilla.org/en-US/kb/fix-problems-images-not-show (Chrome): https://www.makeuseof.com/fix-google-chrome-not-loading-images/
Unfortunately I cannot reproduce this issue locally on Firefox or Chrome. This is a very strange issue that I haven't seen before in the past 3 years of game development. This suggests that the issue is something in your settings / preferences / security options in the browsers. Or the way the HTML is launched.
If you've checked the above browser settings, and it still isn't working, can check the console logs of the page? In firefox: First open the html. Then press Ctrl + Shift + J (in Windows) or Cmd + Shift + J (in Mac). Then refresh the html by pressing F5 or Ctrl + R. Does the console output mention anything about images / png files not loading properly?
