styleKey = function (key) {
        key.el.style.display = 'inline-block';
        key.el.style['-webkit-user-select'] = 'none';

        if (key.colour === 'white') {
            styleWhiteKey(key);
        } else {
            styleBlackKey(key);
        }
    }
Add styling to individual key on keyboard.
@param  {object} key Element of key.