Add Helm Chart configuration table reference to installation guide (#1452)

* Add Helm Chart configuration table reference to installation guide

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.

* Update Helm README link to main branch, amend release process document

Author: ADubhlaoich

docs/developer/release-process.md

@@ -44,7 +44,7 @@ To create a new release, follow these steps:
        file.
     5. Generate the installation manifests by running `make generate-manifests`.
     6. Modify any `git clone` instructions to use `vX.Y.Z` tag.
-    7. Modify any docs links that refer to `main` to instead refer to `vX.Y.Z`.
+    7. Modify any docs links that refer to `main` to instead refer to `vX.Y.Z` or `release-x-y`, whichever is applicable.
     8. Update any installation instructions to ensure that the supported Gateway API and NGF versions are correct.
        Specifically, helm README and `site/content/includes/installation/install-gateway-api-resources.md`.
     9. Update the [README](/README.md) to include information about the release.

site/content/installation/installing-ngf/helm.md

@@ -215,6 +215,10 @@ Follow these steps to uninstall NGINX Gateway Fabric and Gateway API from your K
 
    - {{<include "installation/uninstall-gateway-api-resources.md" >}}
 
+## Additional configuration
+
+For a full list of the Helm Chart configuration parameters, read [the NGINX Gateway Fabric Helm Chart](https://github.com/nginxinc/nginx-gateway-fabric/blob/main/deploy/helm-chart/README.md#configuration).
+
 ## Next steps
 
 ### Expose NGINX Gateway Fabric