ci: explicitly install SBT (removed from GitHub in newer Ubuntu version) (#37)

Author: JavierCane

.github/workflows/ci.yml

@@ -19,6 +19,7 @@ jobs:
           distribution: 'zulu'
           java-version: '21'
           cache: 'sbt'
+      - uses: sbt/setup-sbt@v1
       - name: 👌 Run "pre-push" tasks (compile and style-check)
         run: sbt prep
       - name: ✅ Generate a project and run its test