HACKING: Use syntax highlighting

This makes it a bit nicer to read in gitlab while still looking o.k. in
an editor.
3 jobs for syntax-hl in 7 minutes and 20 seconds (queued for 1 second)
Status Name Job ID Coverage
  Build
passed build-debian-clang #3539
librem5

00:02:51

passed build-debian-gcc #3538
librem5

00:02:13

24.9%
passed build-debian-package #3540
librem5

00:02:15