Add GitHub Actions CI workflow

.github/workflows/ci.yml

@@ -0,0 +1,35 @@
+name: CI
+
+on:
+  pull_request:
+    branches:
+      - master
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v3
+
+      - name: Set up JDK 8
+        uses: actions/setup-java@v3
+        with:
+          distribution: temurin
+          java-version: '8'
+
+      - name: Cache Gradle dependencies
+        uses: actions/cache@v3
+        with:
+          path: |
+            ~/.gradle/caches
+            ~/.gradle/wrapper
+          key: ${{ runner.os }}-gradle-${{ hashFiles('**/*.gradle*', 'gradle/wrapper/gradle-wrapper.properties') }}
+          restore-keys: |
+            ${{ runner.os }}-gradle-
+
+      - name: Set executable permission for gradlew
+        run: chmod +x gradlew
+
+      - name: Build with Gradle
+        run: ./gradlew build --console=plain