post_grid_share_buttons

add_filter('post_grid_share_buttons', 'post_grid_share_buttons_custom', 90, 2);

function post_grid_share_buttons_custom($share_button_html, $args)
{
    $element  = isset($args['element']) ? $args['element'] : array();

    $post_id = isset($args['post_id']) ? $args['post_id'] : '';
    $post_title = get_the_title($post_id);
    $post_link = get_permalink($post_id);

    $link_target = isset($element['link_target']) ? $element['link_target'] : '';

    $share_button_html .= '
		<span class="fb">
			<a target="' . $link_target . '" href="https://www.facebook.com/sharer/sharer.php?u=' . $post_link . '"><i class="fab fa-facebook-square"></i></a>
		</span>
		<span class="twitter">
			<a target="' . $link_target . '" href="https://twitter.com/intent/tweet?url=' . $post_link . '&text=' . $post_title . '"><i class="fab fa-twitter-square"></i></a>
		</span>';

    return $share_button_html;
}