Set up CI with GitHub Actions

.github/workflows/gradle.yml

@@ -0,0 +1,34 @@
+name: Java CI
+
+on: [push, pull_request]
+
+jobs:
+  build:
+    strategy:
+      matrix:
+        platform: [ubuntu-latest, macos-latest, windows-latest]
+    runs-on: ${{ matrix.platform }}
+
+    steps:
+      - name: Set up repository
+        uses: actions/checkout@master
+
+      - name: Set up repository
+        uses: actions/checkout@master
+        with:
+          ref: master
+
+      - name: Merge to master
+        run: git checkout --progress --force ${{ github.sha }}
+
+      - name: Validate Gradle Wrapper
+        uses: gradle/wrapper-validation-action@v1
+
+      - name: Setup JDK 17
+        uses: actions/setup-java@v1
+        with:
+          java-version: '17'
+          java-package: jdk+fx
+
+      - name: Build and check with Gradle
+        run: ./gradlew check