Add GitHub Actions: auto build on push, attach JAR on release

Author: 7yunluo

.github/workflows/build.yml

@@ -0,0 +1,37 @@
+name: Build & Release
+
+on:
+  push:
+    branches: [ master ]
+  pull_request:
+    branches: [ master ]
+  release:
+    types: [ published ]
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Set up Java 21
+        uses: actions/setup-java@v4
+        with:
+          java-version: '21'
+          distribution: 'temurin'
+          cache: 'maven'
+
+      - name: Build with Maven
+        run: mvn package -q
+
+      - name: Upload artifact
+        uses: actions/upload-artifact@v4
+        with:
+          name: SeedShield
+          path: target/SeedShield-*.jar
+
+      - name: Upload JAR to Release
+        if: github.event_name == 'release'
+        uses: softprops/action-gh-release@v2
+        with:
+          files: target/SeedShield-*.jar