Add a development mode to allow changes to be picked up even when CSS/JS aggregation is enabled

I think this would be a good idea as a developer mode, we could possibly add it in a similar way to ✨ Make it easier for theme builders to enable Twig debugging and disable render cache Fixed .

Re-titling since CSS and js aggregation have been enabled by default for some time now, so this is more about allowing them to be enabled during development too without requiring cache clears.

I think there's a possible way to do this now that 🐛 Ensure that edge caches are busted on deployments for css/js aggregates Fixed is in 10.1

I think what we'd want, is a setting to disable the caching in AssetResolver::getCssAssets() and AssetResolver::getJsAssets() - this would force the URLs to be generated on every page request. Then unversioned libraries would result in a different URL every time the file changes.

A more aggressive approach would be to do the file_get_contents() check on every file regardless of version when that setting is enabled.