Add Kustomize example with an image built by skaffold

[nkubala]

this just adds a quick example of using skaffold with kustomize on an image being built in the same project.

[codecov]

Codecov Report

Merging #3901 into master will increase coverage by 0.05%.
The diff coverage is n/a.

Impacted Files	Coverage Δ
pkg/skaffold/deploy/resource/deployment.go	90.9% <0%> (-3.69%)	⬇️
pkg/skaffold/deploy/status_check.go	68.3% <0%> (-0.76%)	⬇️
pkg/skaffold/initializer/analyze/builder.go	100% <0%> (ø)	⬆️
pkg/skaffold/build/gcb/cloud_build.go	0% <0%> (ø)	⬆️
cmd/skaffold/app/cmd/init.go	100% <0%> (ø)	⬆️
pkg/skaffold/initializer/analyze/analyze.go	89.28% <0%> (+0.19%)	⬆️
pkg/skaffold/runner/deploy.go	67.85% <0%> (+1.19%)	⬆️
pkg/skaffold/deploy/kustomize.go	73.8% <0%> (+1.3%)	⬆️
pkg/skaffold/build/gcb/jib.go	86.36% <0%> (+2.36%)	⬆️
...affold/kubernetes/portforward/kubectl_forwarder.go	68.29% <0%> (+2.43%)	⬆️
... and 1 more

[balopat]

do you want to add an actual test for it too?