ci: add a shellcheck job

We only have one script (wp-uninstalled.sh) but let's check that.
7 jobs for wip/shellcheck in 6 minutes and 13 seconds (queued for 10 seconds)
Status Name Job ID Coverage
  Container
passed container_fedora #15097479

00:03:27

passed container_ubuntu #15097480

00:00:13

 
  Build
passed build_on_fedora_no_docs #15097482

00:01:29

passed build_on_fedora_with_docs #15097481

00:01:33

passed build_on_ubuntu_no_gir #15097484

00:01:28

passed build_on_ubuntu_with_gir #15097483

00:01:28

 
  Analysis
passed shellcheck #15097485

00:01:11