Extrepo installation instruction

[lgtmak]

Improved instructions for installing xcaddy after enabling the Cloudsmith repository with extrepo (newer best practice for Debian).

[francislavoie]

TIL of extrepo, the repo information is sourced from https://salsa.debian.org/extrepo-team/extrepo-data/-/blob/master/repos/debian/caddyserver.yaml it seems, which is fine I guess, but idk, I'm not sure I like that this repo adds a link to the supply chain. Seems really unnecessary. I also don't like that they call it "caddyserver", that's not the name of the project, it's "caddy" and the "server" part was only necessary because the org and website were already taken. The package is caddy everywhere else.

[mohammed90]

I also don't like that they call it "caddyserver", that's not the name of the project, it's "caddy" and the "server" part was only necessary because the org and website were already taken. The package is caddy everywhere else.

Me neither. I'll try to fix it