fullscreen = function(activate) {
    const spreadsheet = this;

    // If activate not defined, get reverse options.fullscreen
    if (activate == null) {
        activate = ! spreadsheet.config.fullscreen;
    }

    // If change
    if (spreadsheet.config.fullscreen != activate) {
        spreadsheet.config.fullscreen = activate;

        // Test LazyLoading conflict
        if (activate == true) {
            spreadsheet.element.classList.add('fullscreen');
        } else {
            spreadsheet.element.classList.remove('fullscreen');
        }
    }
}
Activate/Disable fullscreen
use programmatically : table.fullscreen(); or table.fullscreen(true); or table.fullscreen(false);
@Param {boolean} activate