[9.x] Add manifestHash function to Illuminate\Foundation\Vite

[innocenzi]

This PR adds a hash method to Illuminate\Foundation\Vite that returns a unique hash if the manifest exists. This is useful to invalidate assets, for instance using Inertia:

<?php

// ...

class HandleInertiaRequests extends Middleware
{

    // ...

    public function version(Request $request): ?string
    {
        return Vite::hash();
    }
}

[timacdonald]

Useful for any long-lived front-end.

Thought: Wonder if Vite::manifestHash() might indicate better what it is doing?

[innocenzi]

@timacdonald Fine by me, I updated the PR 👍

[timacdonald]

Thank you Enzo!