docs: wrong config path for autoloaded .caddyfile (#2059)
Hi !
I am playing with FrankenPHP, and frankly new to the thing so I may be
wrong.
The [current documentation](https://frankenphp.dev/docs/config/#docker)
mention that :
> /etc/frankenphp/caddy.d/*.caddy: additional configuration files that
are loaded automatically
But in the main Caddyfile ([here on
GitHub](https://github.com/php/frankenphp/blob/main/caddy/frankenphp/Caddyfile#L59))
imports differently:
```ini
import Caddyfile.d/*.caddyfile
```
This PR aims to correct this :)
Thank you for your time !
Signed-off-by: Arkeins <7311955+Arkeins@users.noreply.github.com>
