Include polyfill for Node `stream` API to ensure compatibility with Webpack 5

[steveluscher]

This should fix #10.

This library makes use of the stream module. This is a Node API that's no longer polyfilled by Webpack 5.

Anyone who depends upon cipher-base won't be able to upgrade their project to Webpack 5. Webpack will fail to build their project, citing that stream is missing. This also implies that anyone trying to use cipher-base with Create React App 5 won't be able to either, since CRA5 uses Webpack 5.

Here's an example of folks in the Web3 community having trouble with this: https://github.com/solana-labs/wallet-adapter/issues/241

Test plan: yarn test.