fix(chart): add parameter for service.targetPort

[holysoles]

This PR adds a value for service.targetPort. While not explicitly necessary, we do need to pass an APP_PORT env variable to the docker image for the entrypoint script to correctly configure the nginx config file. Otherwise, nginx throws an error about "too many arguments:

nginx: [emerg] invalid number of arguments in "listen" directive in /etc/nginx/nginx.conf:66

Alternatively, we could just populate the APP_PORT env variable with .Values.service.port

[holysoles]

@jessebot FYI this is the last PR i have for now, i was able to get the webserver running with these fixes. I haven't touched any administration or anything yet though

[jessebot]

Thanks for all your hard work! Please just remember to bump the helm chart version and run helm-docs in the future, to speed up the merge process. Really appreciate you hammering this out though! 🙏