Add deployment scripts

[f1ames]

This PR introduces helm chart for admission controller for easier and more flexible deployment.

It focuses on Helm chart only. I would like to cover release related pipeline in a follow-up PR (so building and publishing docker images, packaging and releasing Helm chart, etc).

Changes

• Introduced ./helm directory with helm chart files. It allows for very basic customization (for image used, namespace to which admission controller is deployed and namespaces which should be ignored by it).
• Added very basic integration tests (detached from nodejs code, talking directly to cluster, so can be later used to test install scripts/manifests/charts).
• Reworked skaffold script (used for development) so it uses helm template > file... internally to not duplicate manifests.
• Did some structure changes and README updates.

Fixes

• Changes as above.

Testing

See CONTRIBUTING.md. This still can be only tested with locally build docker images and helm.

Checklist

• [x] tested locally
• [x] added new dependencies
• [x] updated the docs
• [x] added a test

[f1ames]

LGTM but I'd also like Stefan's eyes on the deployment part.

Yes, me too 👍 Waiting for Stefan input then before merging.

[f1ames]

@murarustefaan would you take a look?

[f1ames]

I'm wondering whether we should test agains multiple Kubernetes version. As this is not requesting a specific one, it will vary between minikube releases.

We can run the test in parallel for like the last 3-5 kubernetes version and see the results, as most Kubernetes add-ons in the CNCF space do.

@murarustefaan Could be useful 👍 Do you have any such projects at hand which does that so I can take a look? Do you suggest it could be like `[8 latest major K8s versions x few latest major helm version]? (like K8s 1.20.x - 1.28.x? not sure for Helm 🤔)

EDIT

Run an experiment with such matrix here - https://github.com/kubeshop/monokle-admission-controller/actions/runs/6574236171.

The number of combinations could get high quickly. So either we go with [k8s x helm] (as job above) or multiple k8s version + one helm version and then one k8s version + multiple helm versions. Not exactly sure how one effects the other 🤔

@WitoDelnat @murarustefaan any additional thoughts on this?

[murarustefaan]

I'd say 3 helm versions * last 3-4 kube versions works for now, we also don't want to use a lot of Github Actions time as that will cost us in the longer run.