feat: add helm chart

[DerekTBrown]

What does this PR do?

1. Adds an official Helm chart for Goldpinger, copied from the one published by @okgolove (https://github.com/okgolove/helm-charts/tree/master/charts/goldpinger); also licensed under Apache 2.0.
2. Adds a GitHub Action to publish the Goldpinger chart to GH Pages (will require the GitHub admin to enable some things before this will fully work).
3. Adds a Tiltfile for launching Goldpinger via the Helm chart.
4. Adds a script (called by the Tiltfile) that validates that Goldpinger works as expected on a two-node cluster.
5. Updated the documentation accordingly.

Why do we need this?

1. This will improve the experience of installing Goldpinger for users, since they can install the daemonset with a few commands.
2. This will make it easier to evolve Goldpinger in the future, as there is a shared/default understanding of how it is deployed.

How is this PR tested?

I was able to validate the end-to-end behavior using act:

act -j helm_test --container-architecture linux/amd64 pull_request
...
<success>

I will need someone's assistance testing the release behavior using GitHub Actions, since this is dependent on access to the repo itself.

[skamboj]

Thank you so much for contributing this Helm chart. Apologies it took so long for us to approve it and merge it in. We will setup the publishing of the helm chart.

LGTM,