Optimize auth.js: Replace Buffer.from(x).toString('base64') with btoa

[maslowivan]

Summary

IE10+ browsers support btoa function. Do we really need 50kb Buffer polyfill in the browser?
With this pull request #1650 we can just get rid of the entire Buffer's polyfill

Todo

• Tests
  • Unit
  • Integration
  • Acceptance
• Documentation
• Type label for the PR

[maslowivan]

For ones who using it with Babel/Webpack and a browser, you can hack this using this way:

import SdkAuth, { TokenProvider } from '@commercetools/sdk-auth/dist/sdk-auth.es';

if (typeof Buffer === 'undefined' && typeof window !== 'undefined') {
  window.Buffer = {
    from: s => ({ toString: m => m === 'base64' ? btoa(s) : m }),
    byteLength: s => s.length,
  };
}

[changeset-bot]

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