d/control: Add json-glib-tools as build dependency

This will make sure that the json theme file gets validated in CI.
8 jobs for add_json_tools in 8 minutes and 12 seconds (queued for 1 second)
Status Job ID Name Coverage
  Build
passed #369870
librem5
build:native-debian-bullseye

00:01:17

passed #369868
librem5
build:native-debian-buster:full

00:01:00

passed #369869
librem5
build:native-debian-buster:lib

00:00:58

 
  Test
passed #369871
librem5
test:native-debian-bullseye

00:00:47

62.6%
 
  Package
passed #369872
librem5
package:deb-debian-buster

00:01:06

passed #369873
librem5:arm64
package:deb-debian-buster:arm64

00:04:01

 
  Test Package
passed #369874
librem5
autopkgtest-debian-buster-package

00:02:04

passed #369875
librem5
lintian-debian-buster-package

00:01:01