[12.x] Support Passing Htmlable Instances to Js::from()

[jj15asmr]

This PR adds support for passing Htmlable instances to the Js::from() method. This change also affects the @js() Blade directive as it uses the same underlying method.

Previously, passing an Htmlable instance would result in an empty JSON object being returned:

use Illuminate\Support\{HtmlString, Js};

$data = new HtmlString('<p>Hello, World!</p>');

echo Js::from($data);

// Output: "{}"

This is due to PHP's native json_encode() function not understanding how to convert the instance to a type it can work with (string, in this case).

To fix this, we check if $data is an instance of Htmlable and if so, call the ->toHtml() method on it before encoding. This now gives us the expected result:

use Illuminate\Support\{HtmlString, Js};

$data = new HtmlString('<p>Hello, World!</p>');

echo Js::from($data);

// Output: "'\u003Cp\u003EHello, World!\u003C\/p\u003E'"

I thought this would be useful as I recently needed to pass some sanitized HTML returned as an instance of HtmlString to an Alpine.js component. It removes the extra step of having to call ->toHtml() directly, making the conversion much more seamless.