goreleaser upgrades

Merge pull request #137 from mattfenwick/go-1.21

move to go 1.21, update some deps

Merge pull request #131 from mattfenwick/add-hg-contribs

add huntergregory to contributors

Merge pull request #128 from mattfenwick/go-1.19

Go 1.19

v0.5.0

upgrade to go 1.18

Merge pull request #119 from mattfenwick/labels-diff-hacking

handle default namespace labels in kube 1.21

Merge pull request #116 from mattfenwick/ginkgo

migrate tests into ginkgo framework

add thanks to contributors