write krew manifest file for subctl

[Jaanki]

write a crew manifest file for subctl so that subctl can be installed via Krew. The file needs to be submitted to krew index after 0.16.0 release.

The manifest file would look like this:

apiVersion: krew.googlecontainertools.github.com/v1alpha2
kind: Plugin
metadata:
  name: subm
spec:
  version: "v0.16.0"
  homepage: https://github.com/submariner-io/subctl
  shortDescription: "Manages Submariner and its services"
  description: |
    CLI to install, uninstall and troubleshoot Submariner on a Kubernetes cluster.
  platforms:
    - selector:
        matchLabels:
          os: linux
          arch: amd64
      uri: https://github.com/submariner-io/releases/releases/download/v0.15.0/subctl-v0.15.0-linux-amd64.tar.gz
      sha256: "e5a1ee20019a345a45cb3dcd4f653ea9eb0e34c04f6b6e598bf1294e37359095"
      files:
        - from: subctl*/subctl
          to: .
      bin: subctl

Changes to be made:

1. The URL has to be changed
2. Logic for other OS/Arch needs to be added

Depends on: submariner-io/releases#723

[Jaanki]

Raised a PR: kubernetes-sigs/krew-index#3432

[Jaanki]

Closing as DONE. The above PR is merged. subctl is now available as a krew plugin named subm.

$ kubectl subm version
subctl version: v0.16.2