[Helm] Add snippet to main section of nginx/gateway configuration for adding custom modules

Is your feature request related to a problem? Please describe.

I want to add my own module to nginx/gateway in easy way.

Describe the solution you'd like

Equivalent of httpSnippet or serverSnippet but for adding modules (or other things) in appropriate section of the configuration file, like so (mainSnippet is just a proposition):

        {{- with .Values.gateway.nginx.config.mainSnippet }}
        {{ . }}
        {{- end }}
        worker_processes  5;  ## Default: 1
        error_log  /dev/stderr {{ .Values.gateway.nginx.config.errorLogLevel }};
        pid        /tmp/nginx.pid;
        worker_rlimit_nofile 8192;

        events {
          worker_connections  4096;  ## Default: 1024
        }

        http {

Describe alternatives you've considered

The only alternative is to maintain whole configuration file yourself.