Set up CI using GitHub Actions.

.github/workflows/maven.yml

@@ -0,0 +1,27 @@
+name: Java CI
+
+on: [push]
+
+jobs:
+  build:
+
+    runs-on: ubuntu-latest
+
+    steps:
+    - uses: actions/checkout@v1
+
+    - name: Set up JDK 1.8
+      uses: actions/setup-java@v1
+      with:
+        java-version: 1.8
+
+    - name: Cache Maven dependencies
+      uses: actions/cache@v1
+      with:
+        path: ~/.m2
+        key: build-${{ hashFiles('pom.xml') }}
+        restore-keys: |
+          build-
+
+    - name: Build with Maven
+      run: mvn --batch-mode -show-version --errors package