Add release workflow for automated app deployment

Author: lennartdohmann

.github/workflows/release.yml

@@ -0,0 +1,46 @@
+name: Release App
+
+on: 
+  push:
+    tags: ["*"]
+
+jobs:
+  release:
+    runs-on: ubuntu-latest
+    if: startsWith(github.ref, 'refs/tags/')
+    steps:
+      - uses: actions/checkout@v4
+
+      - uses: actions/download-artifact@master
+        with:
+          name: build-dir
+          path: build/
+
+      - name: write version to output
+        id: write-version-to-output
+        run: |
+          RELEASE_VERSION=${GITHUB_REF#refs/tags/}
+          echo "RELEASE_VERSION=$RELEASE_VERSION" >> $GITHUB_OUTPUT
+
+      - name: Github Release
+        uses: softprops/action-gh-release@v2
+        with:
+          files: build/artifacts/*
+
+      - name: Attach tarball to github release
+        uses: svenstaro/upload-release-action@v2
+        id: attach_to_release
+        with:
+          repo_token: ${{ secrets.GITHUB_TOKEN }}
+          file: ./build/artifacts/gdatavaas.tar.gz
+          asset_name: gdatavaas.tar.gz
+          tag: ${{ github.ref }}
+          overwrite: true
+
+      - name: Upload app to Nextcloud appstore
+        uses: nextcloud-releases/nextcloud-appstore-push-action@v1
+        with:
+          app_name: gdatavaas
+          appstore_token: ${{ secrets.VAAS_APPSTORE_TOKEN }}
+          download_url: ${{ steps.attach_to_release.outputs.browser_download_url }}
+          app_private_key: ${{ secrets.VAAS_NEXTCLOUD_KEY }}