Add maintainers etc. labels to Dockerfile

[pmalek-sumo]

Let's add proper maintainers and description labels to Dockerfile

https://github.com/SumoLogic/sumologic-kubernetes-setup/blob/main/Dockerfile

  "labels": {
    "maintainer": "Fluentd developers <fluentd@googlegroups.com>",
    "Description": "Fluentd docker image",
    "Vendor": "Fluent Organization",
    "Version": "1.11.1"
  }

Incorrect manifest ref: https://github.com/orgs/SumoLogic/packages/container/kubernetes-fluentd/440993