对于字符型的头像，当字符串较长时，字体大小可以根据头像宽度自动调整。也可使用 gap 来设置字符距离左右两侧边界单位像素。
en-US
For letter type Avatar, when the letters are too long to display, the font size can be automatically adjusted according to the width of the Avatar. You can also use gap to set the unit distance between left and right sides.
