Update scala.yml to set up SBT (#311)

Author: balhoff

.github/workflows/scala.yml

@@ -18,5 +18,7 @@ jobs:
       with:
         java-version: '11'
         distribution: 'adopt'
+    - name: Setup SBT
+      uses: sbt/setup-sbt@v1
     - name: Run tests
       run: sbt test