// Theme Shortcodes
// [button text="Click Me" href="/link/" size="sm" target="_self" ]
function berg_button( $atts ) {
    $a = shortcode_atts( array(
        'text' => 'button',
        'href' => '#',
        'size' => 'md',
        'target' => '_self',
    ), $atts );

    if ( ! in_array( $atts['size'], ['sm', 'md', 'lg'] ) ) {
        $atts['size'] = 'md';
    }

    if ( ! in_array( $atts['target'], ['_blank', '_self', '_parent', '_top'] ) ) {
        $atts['target'] = '_self';
    }

    return '<a href="'. $atts['href'] . '" class="theme-button-' . $atts['size'] . '" target="' . $atts['target']
        . '" >' . $atts['text'] . '</a>';
}
add_shortcode( 'button', 'berg_button' );