add GitHub Actions

.github/workflows/gradle.yml

@@ -0,0 +1,28 @@
+name: Java CI with Gradle
+
+on: [push, pull_request, workflow_dispatch]
+
+permissions:
+  contents: read
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v3
+      - name: Set up JDK 8
+        uses: actions/setup-java@v3
+        with:
+          java-version: '8'
+          distribution: 'temurin'
+      - name: Validate Gradle wrapper
+        uses: gradle/wrapper-validation-action@e6e38bacfdf1a337459f332974bb2327a31aaf4b
+      - name: Build with Gradle
+        uses: gradle/gradle-build-action@0d13054264b0bb894ded474f08ebb30921341cee
+        with:
+          arguments: build
+      - name: Archive artifacts
+        uses: actions/upload-artifact@v3
+        with:
+          name: Release files
+          path: build/libs/*.jar