Document installation using proxy set up with user and password

[RIHELO]

Is your feature request related to a problem? Please describe

I was not able to set up proxy in JCasC section of the values.yaml, it does not get rendered and it is not added to the configuration.
If added manually to the rendered file (after helm template) and applied then the installation does not load the file and fails.

Describe the solution you'd like

Please document the installation using proxy setup with username and password, at least as comments in the values.yaml
It took my a lot of time to find that if can be done using the javaOpts and passing -D arguments like this:
-Dhttp.proxyHost=proxy.example
-Dhttp.proxyPort=8080
-Dhttp.user=user
-Dhttp.password=password
-Dhttps.proxyHost=proxy.example
-Dhttps.user=user
-Dhttps.password=password
-Dhttps.proxyPort=8080

Describe alternatives you've considered

I tried to set environment variables, i.e. HTTP_PROXY HTTPS_PROXY, NO_PROXY and never worked.

Additional context

No response