Add GitHub Action to build and attach JAR to release

.github/workflows/release.yml

@@ -0,0 +1,32 @@
+name: Build and Attach JAR to Release
+
+on:
+  release:
+    types: [created]
+
+permissions:
+  contents: write
+
+jobs:
+  build-and-attach:
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Set up JDK 21
+        uses: actions/setup-java@v4
+        with:
+          java-version: '21'
+          distribution: 'temurin'
+
+      - name: Grant execute permission for gradlew
+        run: chmod +x gradlew
+
+      - name: Build with Gradle
+        run: ./gradlew clean build
+
+      - name: Upload JAR to release
+        uses: softprops/action-gh-release@v2
+        with:
+          files: build/libs/Herald-*.jar