Support more kickstart options

[mvo5]

We have the following code in images:

	// Because osbuild core only supports a subset of options, we append to the
	// base here with some more hardcoded defaults
	// that should very likely become configurable.
	hardcodedKickstartBits := `
reqpart --add-boot

part swap --fstype=swap --size=1024
part / --fstype=ext4 --grow

reboot --eject
`

(from https://github.com/osbuild/images/pull/440/files#diff-12a483f85526bab16de723964940dbc6eb71dce708019f7a60c5fcc4f0d478faR440)

So we want to make sure this is supported by osbuild