Update local setup doc to include pointing workspaces proxy domains to load balancer exposed by the ingress controller

Issue: docs: include step to point domains to ingress ... (!7 - closed)

Description

Was having trouble getting local workspaces proxy working. Turns out we're missing a step to update the DNS record in the local setup docs to point ${GITLAB_WORKSPACES_PROXY_DOMAIN} and ${GITLAB_WORKSPACES_WILDCARD_DOMAIN} to the load balancer exposed by the Ingress controller in /etc/hosts file.

Notes

• Retrieve the load balancer IP address by running kubectl get service ingress-nginx-controller -n ingress-nginx -o jsonpath='{.status.loadBalancer.ingress[0].ip}'
• Update /etc/hosts file to point above IP address to ${GITLAB_WORKSPACES_PROXY_DOMAIN} and ${GITLAB_WORKSPACES_WILDCARD_DOMAIN}