Create helm chart to easily deploy to a Kubernetes setup

[batpad]

We need to deploy stac-auth-proxy as part of our eoAPI deployment for IFRC. We would ideally have a published Docker image + Helm chart that we can pull into https://github.com/ifRCGo/monty-eoapi as part of our eoapi-k8s deployment, and configure it to be the primary ingress, proxying requests to stac-fastapi.

I would like to make the following changes here:

• Publish Docker image, refs Publish docker images #5
• Create and publish a Helm chart for the service, with various configuration options that can be defined as part of a values.yaml

We would then use this helm chart to add stac-auth-proxy to our monty-eoapi setup so that we can have a layer of authentication for the Montandon API, as needed by IFRC - we only need authentication based on a JWT token, and no complex authorization rules, so this seems like a good use-case for stac-auth-proxy.

I will go ahead and start working on these changes in a branch. Let me know if there are any concerns or suggestions to do things differently.

@pantierra @alukach @emmanuelmathot