Add workflow to automatically release artifacts

Should help with #74.

.github/workflows/desktop-release.yml

@@ -0,0 +1,45 @@
+name: Automatic Desktop Release
+
+on:
+  push:
+    tags:
+    - 'v*'
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+    - name: Checkout code
+      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 with Gradle
+      run: ./gradlew desktop:dist
+
+    - name: Create release
+      id: create_release
+      uses: actions/create-release@v1
+      env:
+        GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+      with:
+        tag_name: ${{ github.ref }}
+        release_name: ${{ github.ref }}
+        draft: false
+        prerelease: false
+
+    - name: Upload release asset
+      uses: actions/upload-release-asset@v1
+      env:
+        GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+      with:
+        upload_url: ${{ steps.create_release.outputs.upload_url }}
+        asset_path: ./desktop/build/libs/*.jar
+        asset_name: Klooni-${{ github.ref }}.jar
+        asset_content_type: application/java-archive