Add zeitwerk check to CI

This will check if the application is complying with zeitwerk conventions.
https://guides.rubyonrails.org/classic_to_zeitwerk_howto.html

.github/workflows/ci.yml

@@ -9,6 +9,9 @@ concurrency:
   group: ${{ github.workflow }}-${{ github.event.number || github.ref }}
   cancel-in-progress: ${{ github.ref_name != 'main' }}
 
+env:
+  CI: true
+
 jobs:
   scan_ruby:
     runs-on: ubuntu-latest
@@ -109,6 +112,9 @@ jobs:
       - name: Run Syntax Tree
         run: yarn stree-ci
 
+      - name: Run zeitwerk check
+        run: bin/rails zeitwerk:check
+
   test:
     runs-on: ubuntu-latest
     needs: [scan_ruby, lint]