wallet_watchAsset
请求用户在 MetaMask 中添加新的资产。返回一个布尔值，是否已成功添加。

var res = await window.ethereum.request({
"method": "wallet_watchAsset","params": {"type": "ERC20","options": {"address": "0x55d398326f99059fF775485246999027B3197955","symbol": "USDT","decimals": 18,"image": "https://foo.io/token-image.svg"}}
});
console.log(res);