chore: don't forget to build package before deploying it

.github/workflows/main.yml

@@ -61,6 +61,22 @@ jobs:
         python-version: [3.8]
 
     steps:
+    - uses: actions/checkout@v2
+    - name: Set up Python ${{ matrix.python-version }}
+      uses: actions/setup-python@v2
+      with:
+        python-version: ${{ matrix.python-version }}
+    - name: Get tag
+      id: tag
+      run: echo "::set-output name=version::${GITHUB_REF#refs/tags/}"
+    - name: Install dependencies
+      run: |
+        python -m pip install --upgrade pip setuptools wheel
+        python -m pip install twine
+    - name: Build package
+      run: python setup.py sdist bdist_wheel
+    - name: Check the package
+      run: twine check dist/*
     - name: Publish package
       if: github.event_name == 'push' && startsWith(github.ref, 'refs/tags')
       uses: pypa/gh-action-pypi-publish@release/v1