debian: Add dependenies for running xmllint

This also makes sure we have it available during CI
2 jobs for xmllint in 4 minutes and 22 seconds (queued for 16 minutes and 22 seconds)
latest
Status Job ID Name Coverage
  Build
passed #2766
librem5
build-debian

00:02:08

24.6%
passed #2767
librem5
build-debian-package

00:02:14