Preload font files found in Roots Sage 10 (bud.js) manifest.json

filters.php

<?php

use Illuminate\Support\Str;

/**
 * Add `rel="preload"` to font files found in the manifest
 */
add_filter('wp_head', function (): void {
    echo collect(
        json_decode(asset('manifest.json')->contents())
    )->keys()->filter(function ($item) {
        return Str::endsWith($item, ['.otf', '.eot', '.woff', '.woff2', '.ttf']);
    })->map(function ($item) {
        return sprintf(
            '<link rel="preload" href="%s" as="font" crossorigin>',
            asset($item)->uri()
        );
    })->implode("\n");
});

Inspired by the Sage 10 Laravel Mix package: https://github.com/MWDelaney/sage-fonts-preload