docs: clean up s3 examples

[ricellis]

Checklist

• Added tests for code changes or test/build only changes
• Updated the change log file (CHANGES.md) or test/build only changes
• Completed the PR template below:

Description

Clean up the S3 example scripts.

Fixes #694

Approach

• Extende the examples/README.md with additional instructions and details.
• Clean up dependencies
  • Add dependency on latest 2.x @cloudant/couchbackup (docs said it was using the repo version, but the code had been changed when the package became scoped that it wasn't actually using the checked out version - better to just use latest compatibile shipped version).
  • Use latest modular v3 aws-sdk for client-s3, credential-providers, lib-storage
  • Remove dependency on tmp
  • Remove unusued dev-dependencies
• Clean up package.json to update version to 0.0.2 and remove unused script command.
• Update script code for latest aws-sdk changes.
• Add couchbackup event handlers for additional progress/debug.

Schema & API Changes

• "No change"

Security and Privacy

• "No change"

Testing

• N/A example code, but I tested it manually.

Monitoring and Logging

• "No change"

[eiri]

typos, but overall lgtm