Hello
Cloudflared is a tool developed by cloudflare to proxy dns requests via their 1.1.1.1 dns over https.
A docker container for this would allow easy configuration in combination with a pihole container to ensure maximum security
https://docs.pi-hole.net/guides/dns-over-https/
There do already exist some unofficial docker images maintained by unknown people from the community, but considering the security implications of third parties getting access/control over your dns request, i would be much more confident with an image provided by a trusted 3rd party like LinuxServer.io when no official image is maintained by Cloudflare
More information can also be found in Cloudflares developer documentation