Container links require dnsname plugin

I just spent a few hours trying to figure out why the `links:` directive wasn't creating DNS entries on each container (running rootless). I eventually figured out that I didn't have [the `dnsname` plugin](https://github.com/containers/dnsname/) installed, and so the podman network created by compose had `dns_enabled` set to `false`. Once I installed the `dnsname` and recreated the network, the network gateway was offering DNS and everything worked.

I'd like to submit a pull request to add a note about this to some documentation, since I just assumed this behavior would work "out of the box" as it does with docker-compose; I'm just not sure which documentation to update. Does a recommendation to install `dnsname` belong in the podman install instructions (https://podman.io/getting-started/installation), or somewhere else?

Start with the Podman installation instructions linked in the issue and the podman-compose documentation entry points to determine where rootless networking prerequisites are documented. Document that rootless `links:` DNS requires the `dnsname` plugin and recreating the network after installation; done when users can find this requirement before using `links:`.

Written by the indexing model from the issue text.