Add custom functions and variables to Twig

To add a custom function use following filter:

add_filter( 'integration-cds/twig/functions', function( $functions ) {
    $functions['translate'] = new \Twig\TwigFunction(
        'translate',
        function ( $text ) {
            return __( $text );
        }
    );

    return $functions;
}, 10, 1 );

Usage:

{{ translate('Hello') }}

To add a custom variable use following action:

add_action( 'integration-cds/twig/after-globals', function ( $twigEnvironment ) {
    $twigEnvironment->addGlobal( 'today', date( 'm/d/Y' ) );
} );

Usage:

{{ today }}