Update README.md with download as binary example

[muthurathinam]

cc: @MIchaelMainer @darrelmiller

[MIchaelMainer]

We should specify what the other magic strings options are for the responseType argument. Even better, we should have a ResponseType.ts enum with proper comments.

[muthurathinam]

Yeah, its good to have a ResponseType.ts with comments..! Will update this pull request.

[muthurathinam]

@MIchaelMainer

Updated with changes:

1. Added separate ResponseType.ts file which has ResponseTypes declared as enum
2. Updated the same in readme

Comments added for enum in ResponseType.ts will not be available in the corresponding .d.ts and .js files. As this compiler option modification comes in this change. We will recompile this .ts file to have comments in its .d.ts and .js files once we merge above change.

Yes, MicrosoftGraph.ResponseType.DOCUMENT does return a json response.
As mentioned in this pull request

Additional "Bug"
Setting the responseType to Document will result in JSON being returned.
Fetch API doesn't support this feature (whatwg/fetch#16) This return type doesn't really make sense for communicating with Microsoft Graph.