Add GitHub actions

.github/workflows/build.yml

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+name: Java CI with Gradle
+on:
+  push:
+  pull_request:
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v3
+    - name: Set up JDK 17
+      uses: actions/setup-java@v3
+      with:
+        java-version: '17'
+        distribution: 'temurin'
+        cache: gradle
+    - name: Grant execute permission for gradlew
+      run: chmod +x gradlew
+    - name: Build with Gradle
+      run: ./gradlew build

.github/workflows/release.yaml

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+name: Java CI with Gradle
+on:
+  release:
+    types: [published]
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v3
+    - name: Set up JDK 17
+      uses: actions/setup-java@v3
+      with:
+        java-version: '17'
+        distribution: 'temurin'
+        cache: gradle
+    - name: Grant execute permission for gradlew
+      run: chmod +x gradlew
+    - name: Build with Gradle
+      run: ./gradlew build
+    - name: Find correct JAR
+      id: find-jar
+      run: |
+        output="$(find build/libs/ ! -name "*-javadoc.jar" ! -name "*-sources.jar" -type f -printf "%f\n")"
+        echo "::set-output name=jarname::$output"
+    - name: Upload to the GitHub release
+      uses: actions/upload-release-asset@v1
+      env:
+        GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+      with:
+        upload_url: ${{ github.event.release.upload_url }}
+        asset_path: build/libs/${{ steps.find-jar.outputs.jarname }}
+        asset_name: ${{ steps.find-jar.outputs.jarname }}
+        asset_content_type: application/java-archive