Incorrect documentation for Buffer shim

[bcheidemann]

Using the example webpack config results in the Buffer being resolved incorrectly. Webpack resolves Buffer globally to:
{ __esModule: true, default: ... , Buffer: ... }

Fixed by #768

[humphd]

If you use Fixes #768 in your PR description, it will auto-close these.

[bcheidemann]

Thanks, will do this in future 👍