Add CI workflow

.github/workflows/ci.yaml

@@ -0,0 +1,23 @@
+name: Java CI
+
+on: [ push ]
+
+concurrency:
+  group: ${{ github.ref }}
+  cancel-in-progress: ${{ !contains(github.ref, 'main') }}
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout self
+        uses: actions/checkout@v2
+      - name: Set up JDK 11
+        uses: actions/setup-java@v2
+        with:
+          java-version: '11'
+          distribution: 'adopt'
+          architecture: x64
+          cache: maven
+      - name: Build with Maven
+        run: mvn clean install -DskipTests

.gitignore

@@ -21,4 +21,6 @@
 /shims/spark-hive-shims/target/
 /.idea/
 /shims/target/
-/target/
+/target/
+
+**/.DS_Store