#2 Add Nginx proxy as sidecar to expose Peertube

Hello, As done in the official docker-compose file (See Peertube [#2531](https://github.com/Chocobozzz/PeerTube/pull/2531)), the official nginx configuration shipped with Peertube contains optimisations While it's not necessary for Peertube to work, it would be interesting to have it in the Kubernetes deployment. We may use a Nginx sidecar for that, using a configmap and exposing itself the port 9000 instead of Peertube. We may add an option to enable or not this sidecar. Objective is the cluster configuration (especially the ingress configured and used by the Ops) do not need changes while this feature is enabled or not. To achieve that: - Use same port 9000, exposing the Nginx or Peertube directly - Liveness probes should check Peertube and Nginx correctly - Nginx sidecar should wait for Peertube before reporting READY (using some InitContainer?)