Note: I think this is a bug fix ... but maybe you prefer to consider it a new feature.

The current Symfony Profiler works like this:

• If you don't set the theme, it selects it automatically form light/dark to match your OS
• But you can also select "light" or "dark" explicitly

The problem is that when you choose a theme explicitly, the "auto" theme is no longer available. You need to delete the local storage of your browser.

This PR makes it explicit the "auto theme" already available in the Profiler. That way, you can set "light", "dark" or "auto" explicitly:

It also changes the "theme listener" to respond instantly to OS changes, without having to refresh the page.