window.onbeforeunload does not work on iOS/iPadOS

[lorenzocorallo]

Description

Doing some tests in the PR #72, it was discovered that the window.onbeforeunload event handler, used to prevent page reload while doing the test, does not work on iOS and iPadOS.
This method has been used for a long time, so the website has probably always suffered from this problem, but there seem to have been no previous reports.
At the moment, no fix has been found, also because of the lack of methods to detect Apple mobile devices accurately and to interrupt page reload with a prompt.

Steps to reproduce

1. Open the website using an iOS device
2. Enter the test section (using the start button in the homepage)
3. Reload the page
   If this bug applies, the page should reload and not ask to confirm exit.

Expected behaviour

The event handler window.onbeforeunload (or any other future alternative) should ask the user to confirm to exit the test.

Notes

If a solution is not found in the near future, feel free to close this issue as stale

[EndBug]

Can reproduce on iPhone 13 via BrowserStack 🐛