Clean up Documentation

[josephlewis42]

The documentation for this plugin could be greatly improved. General steps to achieve it:

• [ ] Remove documentation in code, this is no longer recommended for new Logstash plugins because it leads to out-of-sync docs.
• [ ] Make the example config runnable if the user copy/pastes, right now it has extra info (required), (optional) which need to be deleted
• [ ] Provide example configuration for common use-cases to onboard faster and provide guidelines.
• [ ] Add a section for extra resources including pricing, different storage types, ADC and service accounts.
• [ ] Add documentation about minimal service account permissions needed to run the plugin.
• [ ] Remove the TODOs/feature requests and add them as issues in Github.