Adding more examples

[LeonStoldt]

Hi, i stumbled upon this repository yesterday and I really like the idea of providing / sharing docker-compose sample files. That is why I would love to share my docker-compose files, which I am using for my homelab setup.

I would offer the following examples:

• [x] Pi-hole / cloudflared example for use of DNS over HTTPS
• [x] postgreSQL / pgAdmin example
• [x] portainer example
• [x] Plex example
• [x] wireguard example

I hope this can be helpful and I will provide a pull request for review.