CI: Check for missing files in POTFILES.in

Part-of: <https://gitlab.gnome.org/Incubator/loupe/-/merge_requests/188>

.gitlab-ci.yml

@@ -85,6 +85,14 @@ cargo-audit:
     - cargo install cargo-deny
     - cargo deny check
 
+other-checks:
+  interruptible: true
+  image: alpine
+  script:
+    - apk add --no-cache git
+    - git ls-files 'src/*.rs' 'src/*.ui' 'data/*.ui' 'data/*.desktop.in*' '*.metainfo.xml.in*' > po/POTFILES.in
+    - git diff --exit-code
+
 pages:
   stage: deploy
   tags: