Ubuntu Focal template

I've just put in PRs which will fix the issue with sound in Ubuntu

You can build an updated qubes-core-agent with that PR, or grab the
package I've built from https://qubes.3isec.org/
If you want a pre-built template, there's one available for 4.0 at
The templates are signed with my Qubes signing key - make sure you
verify this key, and then verify the rpm package.
Once you've confirmed the package, copy it to dom0, and install it with
`dnf install qubes-template....`

As always, it would be better if you built the template yourself using
the Qube Builder, but if you are reluctant or short of time, feel free
to use the template.
Any problems, let me know.