better-route: custom REST routes

Register the complete router during rest_api_init and declare the access intent of every route.

Minimal public route

use BetterRoute\Http\Response;
use BetterRoute\Router\Router;

add_action('rest_api_init', static function (): void {
    $router = Router::make('myapp', 'v1');

    $router->get('/ping', static fn (): Response => Response::ok(['pong' => true]))
        ->publicRoute();

    $router->register();
});