[Proposed Feature] Implement ListBucket Endpoint

Description of Feature:

Currently we don't implement the S3 "ListBucket" operation which causes some confusion when running the aws s3 ls command (#15). We should implement this endpoint and the natural response for this operation should include all of the Source Cooperative accounts which have repositories as bucket responses.

For example: there are three repositories on Source Cooperative (foo/bar, hello/world, and radiantearth/landcovernet).
The response should be something like this:

> aws s3 ls
2020-06-30 19:31:19 foo
2023-01-02 14:12:41 hello
2024-11-09 17:20:43 radiantearth

What value is this feature adding to Source Cooperative?

Users can navigate the entirety of the Source Cooperative collection of repositories using simple the AWS CLI