Add Helm Chart configuration table reference to installation guide

[ADubhlaoich]

Proposed changes

This commit adds a prominent section to the documentation's Helm installation guide to direct a reader to the Helm README which has all of its configurable parameters.

This information is being referenced instead of duplicated to avoid drift, which has the side-effect of making the Helm chart itself a single source of truth.

Checklist

Before creating a PR, run through this checklist and mark each as complete.

• I have read the CONTRIBUTING doc
• I have added tests that prove my fix is effective or that my feature works
• I have checked that all unit tests pass after adding my changes
• I have updated necessary documentation
• I have rebased my branch onto main
• I will ensure my PR is targeting the main branch and pulling from my branch from my own fork

[ADubhlaoich]

As a point of possible change/discussion: it links to the current release branch/tag for the Helm Chart README.

I intend to create a cherry-pick to the release branch after this has been created: this means that the link is valid to the live release, though I'm unsure if the release process has a version bumping mechanism like NGINX Ingress Controller does.

We could link to the Helm website where the README is displayed instead.

[sjberman]

Right now in our main branch we just link to the main branch for all the things. Then in the release branch, we manually update those links to point to the release branch.

There's definitely room for improvement with this process, ideally some sort of automation, but that hasn't been figured out yet.

[ADubhlaoich]

@sjberman Will I change it to target main for the time being, then?

I can probably dig up the script NGINX Ingress Controller used for the bump (It's now a GitHub Action IIRC) if that's of any use for future reference.

[sjberman]

Per that last point, would you be able to update the release process doc, specifically point 8.7 to say "Modify any docs links that refer to main to instead refer to vX.Y.Z or release-x-y, whichever is applicable."

[sjberman]

@sjberman Will I change it to target main for the time being, then?

I would say yes, for now.

[ADubhlaoich]

Changes requested made.