Kh/npm corrections

[kobyhallx]

As a developer
I would like to use @noir-lang/* packages in browser and nodejs
so that I don't have to maintain separate code bases.

Changes supporting this case:

• barretenberg.js/exports/index.mjs index file supporting ESM style of usage, eg. import ... from ...

• barretenberg.js/package.json

  • adds yarn package script to emit both ESM and CommonJS package versions into their own directories (dest commonjs folder kept for compatibility with previous code)
  • specifies exports and main files according to import/require style
  • adds browser main file
  • barretenberg.js/src/crypto/random/index.ts checks for self first as otherwise window check fails when running in WebWorker, adds an error to make debugging problems a bit easier

• barretenberg.js/src/index.ts adds index with exports for compatibility

• barretenberg.js/src/iso_fetch/index.ts again using self first to avoid execution problems in WebWorker

• barretenberg.js/src/wasm/barretenberg.wasm pre-built wasm binary

• barretenberg.js/src/wasm/barretenberg_wasm.ts relies on import.meta for loading wasm in browser environment, patches this when building for CommonJS

• barretenberg.js/src/wasm/index.ts relies on import.meta for loading wasm in browser environment, patches this when building for CommonJS

• barretenberg.js/src/wasm/worker_factory.ts relies on import.meta for loading wasm in browser environment, patches this when building for CommonJS, branches differently for node and browser as ThreadJS does not support this way of handling workers (attempts to fix path).