S3 operations in @coedl/ocfl-js

[marcolarosa]

I've implemented a bunch of s3 operations that you might find useful in your lib.

I don't know if they're final and unchanging as i'm now reworking the repo/ocfl libs to handle s3 backends but it might be useful to start from.

See https://github.com/CoEDL/ocfl-js/blob/master/lib/s3.js and https://github.com/CoEDL/ocfl-js/blob/master/lib/s3.spec.js

Be sure to add:

"dependencies": {
    "@aws-sdk/client-s3": "^3.3.0",
  },
  "devDependencies": {
    "chance": "^1.1.7",
  }