Add guest capabilities file for Rocky Linux

[evenreven]

Thanks for creating this great plugin!

This PR adds guest capabilities file for Rocky Linux 8. It's basically a copy/paste job from the :centos_8 part of the centos capabilities, but with the 6 and 7 case/when statement removed since it doesn't apply to Rocky (which launched with version 8).

Let me know if this lacks something or is incomplete in some way.

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My setup (if it's relevant):

Since vagrant-libvirt doesn't work with the upstream package on Fedora 35 (and the Fedora-provided package is 2.2.16 (which doesn't support Rocky guests)), I built a Vagrant Podman container like this: ```bash #!/bin/bash -x container=$(buildah from "fedora:rawhide") buildah run "$container" -- dnf install -y openssh-server openssh-clients vagrant vagrant-libvirt buildah run "$container" -- dnf clean all buildah commit "$container" "vagrant" ``` Then after executing this, I run the container: ```bash podman run --rm -it \ --volume /run/libvirt:/run/ \ --volume "${HOME}:${HOME}:rslave" \ -v $SSH_AUTH_SOCK:$SSH_AUTH_SOCK \ -e SSH_AUTH_SOCK=$SSH_AUTH_SOCK \ --env "HOME=${HOME}" \ --workdir "$(pwd)" \ --net host \ --privileged \ --security-opt label=disable \ localhost/vagrant:latest ``` Then I installed my locally built gem inside the container with `vagrant plugin install ./vagrant-sshfs-1.3.6.gem`. Relevant part of my Vagrantfile: ```ruby Vagrant.configure("2") do |config| config.vm.box = "generic/rocky8" config.vm.network :forwarded_port, guest: 3000, host: 3000 config.vm.network :private_network, type: "dhcp" config.ssh.forward_agent = true config.vm.synced_folder ".", "/vagrant", type: "sshfs" config.vm.provider :libvirt do |lv| lv.qemu_use_session = false end end ```

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