Add support for installing kubectl-sync via krew

[rocktavious]

https://krew.sigs.k8s.io/docs/developer-guide/plugin-manifest/
https://krew.sigs.k8s.io/docs/developer-guide/example-manifests/
https://goreleaser.com/customization/krew/

Currently you have to install the kubectl-sync tool via homebrew brew install opslevel/tap/kubectl but the more native thing is to allow for installation via krew kubectl krew install opslevel or kubectl krew install opslevel-sync

2 Customers have asked for this in a low urgency manner

AC

• some form of kubectl krew install ... works