Thank you very much for the tip with the zipping (did not think about this in my hurry...).
No need to thank for the web build: I always wanted to try the html export functionality of Godot. But it always requires the files to be on a server (and a local one is to much of a hassle to set up). So the game jam upload to itch.io was a welcome excuse to try it out :-)
Yes, it is my first game on itch.io and the first Godot game I brought to a somewhat playable state.