Automatically create the package after a release

And then upload it to the created release.
One less step during the release process 💪

We are using that GitHub Actions: https://github.com/shogo82148/actions-upload-release-asset

I've also:
- updated the release script to clone the repo using `https` instead of `git` (otherwise it failed during the build)
- use `md5sum` instead of `md5` because the latest isn't available in GitHub Actions

.github/workflows/upload-release-package.yml

@@ -0,0 +1,39 @@
+name: "Upload release package"
+
+on:
+  release:
+    types:
+      - created
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+
+    strategy:
+      matrix:
+        php:
+          - "7.4"
+
+    steps:
+      - name: "Checkout"
+        uses: "actions/checkout@v3"
+
+      - name: "Install PHP"
+        uses: "shivammathur/setup-php@v2"
+        with:
+          coverage: "none"
+          php-version: "${{ matrix.php }}"
+          tools: pecl, composer:2.2
+          extensions: pdo, pdo_mysql, pdo_sqlite, pdo_pgsql, curl, imagick, pgsql, gd, tidy
+          ini-values: "date.timezone=Europe/Paris"
+        env:
+          COMPOSER_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+
+      - name: Create the package
+        run: make release VERSION=${{ github.event.release.tag_name }}
+
+      - name: Upload the package to the release
+        uses: shogo82148/actions-upload-release-asset@v1
+        with:
+          upload_url: ${{ github.event.release.upload_url }}
+          asset_path: /tmp/wllbg-release/wallabag-${{ github.event.release.tag_name }}.tar.gz