Add yard CI task

Author: bdurand

.github/workflows/continuous_integration.yml

@@ -27,6 +27,7 @@ jobs:
         include:
           - ruby: "ruby"
             standardrb: true
+            yard: true
           - ruby: "3.4"
             appraisal: "activerecord_8.0"
           - ruby: "3.2"
@@ -65,3 +66,6 @@ jobs:
     - name: standardrb
       if:   matrix.standardrb == true
       run:  bundle exec rake standard
+    - name: yard
+      if: matrix.yard == true
+      run:  bundle exec yard --fail-on-warning