Export Token types from core.d.ts

[trivikr]

Fixes: #4291

Testing

Installed local aws-sdk from workspace

$ aws-sdk-js> npm pack

$ test> npm install ../aws-sdk-js/aws-sdk-2.1263.0.tgz

Verified that correct types are exported:

import AWS from "aws-sdk";

const token = new AWS.Token({ token: "token" });
const ssoTokenProvider = new AWS.SSOTokenProvider({ profile: "test" });
const staticTokenProvider = new AWS.StaticTokenProvider({ token: "token" });
const tokenProviderChain = new AWS.TokenProviderChain([]);

Checklist

• .d.ts file is updated
• changelog is added, npm run add-change