Document how to run a popular public instance

[unixfox]

We will specialize only for docker based installations according to the official documentation, but with a notice that a similar setup could be replicated outside of docker or on another system like kubernetes.

What to document:

• The usage of http3-ytproxy in invidious: https://github.com/TeamPiped/http3-ytproxy
• Multiple processes of invidious at the same time with rolling restart. (caddy-docker-proxy?)
• Often restart invidious
• pgbouncer

Advanced documentation (not a priority):

• High availability of postgres

[delgh1]

Postgres: I recommend Citus plugin