Add workflow for Python.

.github/workflows/python.yml

@@ -0,0 +1,66 @@
+name: Python
+
+on:
+  push:
+    branches: [ python ]
+    tags: [ py* ]
+
+jobs:
+  python-build:
+    strategy:
+      matrix:
+        pyver:
+          - "3.6"
+          - "3.7"
+          - "3.8"
+          - "3.9"
+          - "3.10"
+        os:
+          - ubuntu-latest
+          - macos-latest
+          - windows-latest
+    runs-on: ${{ matrix.os }}
+    env:
+      TWINE_USERNAME: ${{ secrets.TWINE_USERNAME }}
+      TWINE_PASSWORD: ${{ secrets.TWINE_PASSWORD }}
+    steps:
+      - uses: actions/checkout@v2
+      - run: git submodule update --init extlib/mimalloc
+      - uses: actions/setup-python@v2
+        with:
+          python-version: ${{ matrix.pyver }}
+      - name: Build and test
+        working-directory: cython
+        run: |
+          python -m pip install -U pip setuptools wheel build
+          python -m pip install -e .
+          python -m unittest
+      - name: Pack
+        working-directory: cython
+        run: python -m build
+      - if: matrix.os == 'ubuntu-latest'
+        name: Upload artifact
+        uses: actions/upload-artifact@v2
+        with:
+          name: ${{ matrix.os }}-py${{ matrix.pyver }}
+          path: cython/dist/*.tar.gz
+      - if: matrix.os != 'ubuntu-latest'
+        name: Upload artifact
+        uses: actions/upload-artifact@v2
+        with:
+          name: ${{ matrix.os }}-py${{ matrix.pyver }}
+          path: cython/dist/*.whl
+      - if: startsWith(github.ref, 'refs/tags/py')
+        run: python -m pip install twine
+      - if: startsWith(github.ref, 'refs/tags/py') && matrix.os == 'ubuntu-latest'
+        name: release
+        working-directory: cython
+        run: |
+          python -m build --sdist
+          python -m twine upload "dist/*.tar.gz" --skip-existing
+      - if: startsWith(github.ref, 'refs/tags/py') && matrix.os != 'ubuntu-latest'
+        name: release
+        working-directory: cython
+        run: |
+          python -m build --wheel
+          python -m twine upload "dist/*.whl" --skip-existing