Add Redis service container to CI workflow

The next commit will add tests that require a local Redis server on the
default port (6379).

Author: smfeest

.github/workflows/ci.yml

@@ -8,6 +8,11 @@ jobs:
     runs-on: ubuntu-22.04
     env:
       WEB_PROJECT_PATH: src/Buttercup.Web
+    services:
+      redis:
+        image: redis
+        ports:
+          - 6379:6379
     steps:
       - name: Checkout
         uses: actions/checkout@v4