ci: Run pipelines for the `ruby3` branch

Signed-off-by: Rémy Coutable <remy@rymai.me>

.gitlab-ci.yml

@@ -49,6 +49,11 @@ workflow:
     - if: '$CI_COMMIT_BRANCH == $CI_DEFAULT_BRANCH && $CI_PIPELINE_SOURCE == "schedule" && $SCHEDULE_TYPE == "maintenance"'
       variables:
         CRYSTALBALL: "true"
+    # Run pipelines for ruby3 branch
+    - if: '$CI_COMMIT_BRANCH == "ruby3"'
+      variables:
+        RUBY_VERSION: "3.0"
+        NOTIFY_PIPELINE_FAILURE_CHANNEL: "f_ruby3"
     # For `$CI_DEFAULT_BRANCH` branch, create a pipeline (this includes on schedules, pushes, merges, etc.).
     - if: '$CI_COMMIT_BRANCH == $CI_DEFAULT_BRANCH'
     # For tags, create a pipeline.