Release server.jar with GHA

.github/workflows/release_server.yml

@@ -0,0 +1,30 @@
+name: Release server
+
+on:
+  release:
+    types: [published]
+
+jobs:
+  build:
+
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: actions/checkout@v2
+      - name: Set up JDK 1.8
+        uses: actions/setup-java@v1
+        with:
+          java-version: 1.8
+      - name: Grant execute permission for gradlew
+        run: chmod +x gradlew
+      - name: Build server
+        run: ./gradlew server:build
+      - name: Release artifact
+        uses: actions/upload-release-asset@v1
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+        with:
+          upload_url: ${{ github.event.release.upload_url }}
+          asset_path: server/build/libs/server.jar
+          asset_name: server.jar
+          asset_content_type: application/zip