improve tailwind config to also catch dynamic classes

[jheuel]

The previous tailwind config did not catch classes that are set dynamically, e.g.

use leptos::*;

fn main() {
    mount_to_body(|| {
        view! { <p
            class:text-orange-600=true
        >"This text should be orange"</p> }
    })
}

would not add text-orange-600.

The tailwind config now uses the content.transform property to transform the leptos code enough for tailwind to extract all classes. Furthermore, there is now a button in all tailwind examples with a dynamic class.

Fixes #2890

[jheuel]

Apologies, when I first opened the pull request I forgot to change the end2end tests. Should be fine now.

[gbj]

Awesome! Thanks very much.

[maxbergmark]

@jheuel I'm a bit late to the party, but thanks for fixing this issue that I opened a while ago!