text:要生成二维码的文本内容(必须)
size:生成二维码大小,单位像素
示例:?text=https%3A%2F%2Fapi.2xb.cn%2FQRCode&size=250
html中调用:<img src=https://api.2xb.cn/QRCode?text=https%3A%2F%2Fapi.2xb.cn%2FQRCode&size=250">