noahdarveau/buffer removal

[noahdarveau-MSFT]

This PR replaces use of the Buffer package with uint8array-extras. This change allows for the removal of the buffer polyfill, which was previously required as Buffer was not supported in browsers. Since uint8array-extras is browser-compatible we do not need to include a polyfill for it. The Buffer polyfill is rather large, ~22KB when minified, and cannot reap the benefits of treeshaking since polyfills are always included in the global scope. We are only using the Buffer package in the clipboard capability, so even if a consumer was treeshaking out clipboard, they were still getting the Buffer polyfill included in their bundle, even though it was not doing anything. With this change, anyone not using the clipboard capability should see a flat ~22KB package size reduction.

To include this package, despite it being and NPM package, it was having issues working with Jest for our tests. I'm still not entirely sure what exactly the issue was, but copying the package locally and running it through our typescript transpiler fixed the issue. There was another issue with TextDecoder not being supported in jsdom, even though it is supported in both Node and browsers, so I included a jest-setup file that polyfills TextDecoder with the Node implementation.

[TrevorJoelHarris]

Couple of small questions and I want to follow up with jay about the transpiled uint8array-extras folder