fix: stylesheet loading

[benjaminrobinet]

Description

This PR aims to fix the loading of Stylesheets.
Currently they are cloned before inserted to the current page, but the one that is awaited to be loaded is not the cloned one. So it never loads.
I am fixing this by returning the newly cloned one.

It also fix the infinite loop / memory leak in the waitForStylesheet function that occurs when the provided timeout is elapsed and the stylesheet never loads.

Checks

• The PR is submitted to the master branch
• The code was linted before pushing (npm run lint)
• All tests are passing (npm run test)
• New or updated tests are included
• The documentation was updated as required

[benjaminrobinet]

Special thanks to @Nam-Hai for helping me on this.

[daun]

Welcome and thanks for contributing. This looks great! Never realized this was broken in the first place. Tests are passing, but I'll give this a try in our playground and report back.

[daun]

Works great, thanks a lot! I realize now why we never caught this. We were testing locally with a delayed stylesheet that was delayed by the same amount as the timeout (😭), so the stylesheet and timeout would trigger at the same time and we just assumed it was the stylesheet when it was the timeout triggering things. We'll try to come up with a set of matching tests.

[benjaminrobinet]

I was so struggling with this issue hahaha, was a pleasure to fix it.
I like how Swup handles the page transitions, thanks for your work !

[daun]

Released as 2.3.1 🥬