add setup-sbt

Author: xuwei-k

.github/workflows/ci.yml

@@ -18,4 +18,5 @@ jobs:
       with:
         java-version: "${{ matrix.java }}"
         distribution: adopt
+    - uses: sbt/setup-sbt@v1
     - run: sbt -v scalafmtSbtCheck "+ scalafmtCheckAll" "+ test"