Create bucket in default region if it doesnt exist

[justinmchase]

If the bucket doesn't exist already, create it.

[jacobheun]

I think this would be good to be configurable as people may not want to inadvertently create Buckets. Perhaps taking from the datastore-fs logic and using createIfMissing:

const store = new S3Store('.ipfs/datastore', {
  s3: s3Instance,
  createIfMissing: false  // defaults to true (mimic datastore-fs)
})

Also, it might be good to put the logic in open and not put since it's only needed when the repo starts.

[justinmchase]

Yeah, sounds good. I'll add that tonight.

[justinmchase]

I added tests and documentation and manually tested locally.

[jacobheun]

LGTM!