[Site] Load importmap polyfill conditionnaly

[smnandre]

With importmap support now over 90% of total usage.. i think we can try something here :)

[smnandre]

Poke @javiereguiluz symfony/symfony#52939

[weaverryan]

@smnandre do you need anything from me on this? Like a deploy of a dev environment to test? Ultimately, I'd like to move this to a PR on Symfony :)

[smnandre]

We need something to test things with non-compatible browsers...

Cannot find it anymore on Slack, but I suggested to get a BrowserStack / similar account.

(on this website... to be honest, i'd skip polyfill entirely with overall support over 92% and this website beeing browsed almost only by tech working visitors haha)

[javiereguiluz]

The code used here is minimal and won't easily change ... so I'd say we don't need to test it in a real legacy browser.

[smnandre]

The code used here is minimal and won't easily change ... so I'd say we don't need to test it in a real legacy browser.

But i'd like to be sure it's working ... and my first attempt did not (because HTMLScriptElement.supports was not available on old browser).

We also (and i'm almost not kidding) can merge this, test live on ux.symfony.com and wait for people experiencing bug, and then fix/built on that.

The last experiments i've done with AssetMapper showed me that the polyfill performance cost is far from minor (at least for someone so crazyfocused on performances).

So believe me when i say i'm the first one wanting to remove it for the vast majority of users that do not need it :)

[weaverryan]

Thanks! Let's deploy and try it out