Allow configuring all the configurable envs from helm values

It is not good to handle the extra config of the application using an array because you can't benefit from the default parameters.

Example:
```
extraEnv:
  - name: MVIEWERSTUDIO_URL_PATH_PREFIX
    value: mviewerstudio
```

It's better to allow configuring all the envs from a helm value: https://github.com/mviewer/mviewerstudio/blob/master/docker/readme.md?plain=1#L6-L12