Add `/admin` entry point in lando config

[SlimDeluxe]

When starting the lando instance, the URLs should include a direct link to the admin panel, e.g. https://eclipse-test.lndo.site/admin

Adding this setting in the lando file does not work — the URL just opens the app public page and not the panel.

proxy:
  appserver_nginx:
    - eclipse-test.lndo.site/admin