Fix/port forward

[ameier38]

PR Checklist

• [x] Chart Version bumped
• [x] Chart packaged and index updated (you can use ./release)
• [x] CHANGELOG.md updated
• [x] Variables and other changes are documented in the README.md

What this PR does / why we need it:

• Add admin.hostname value to handle redirect of root admin endpoint to make port forwarding work better. This is used in the nginx config with proxy_redirect

Maybe there is a better way to get the hostname using nginx variable 🤔 ? I couldn't seem to find any other way to get this to work.

Which issue this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close that issue when PR gets merged):

• fixes #43
• related: https://github.com/EventStore/EventStore/issues/1984

Special notes for your reviewer: @thefringeninja