Fix issue #52

[burgyl]

Fix issue Cannot find name 'ReadableStreamDefaultReadResult' #52

let result: ReadableStreamDefaultReadResult<Uint8Array>;

https://github.com/Azure/fetch-event-source/blob/1589ec1f49d96450f3bae9adb20ab4a5b3deb204/src/parse.ts#L24C61-L24C61

> @microsoft/fetch-event-source@2.0.1 build
> tsc && tsc -p tsconfig.esm.json

src/parse.ts:24:17 - error TS2552: Cannot find name 'ReadableStreamDefaultReadResult'. Did you mean 'ReadableStreamDefaultReader'?

24     let result: ReadableStreamDefaultReadResult<Uint8Array>;
                   ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

  node_modules/typescript/lib/lib.dom.d.ts:11665:13
    11665 declare var ReadableStreamDefaultReader: {
                      ~~~~~~~~~~~~~~~~~~~~~~~~~~~
    'ReadableStreamDefaultReader' is declared here.


Found 1 error in src/parse.ts:24