Build wheels for Python 3.9 too

.github/workflows/build-linux-wheels.yml

@@ -10,7 +10,7 @@ jobs:
     - name: Build manylinux1 Python wheels
       uses: RalfG/python-wheels-manylinux-build@0c24cb31441c7a1e6ea90d6a6408d406b2fee279
       with:
-        python-versions: 'cp35-cp35m cp36-cp36m cp37-cp37m cp38-cp38'
+        python-versions: 'cp35-cp35m cp36-cp36m cp37-cp37m cp38-cp38 cp39-cp39'
     - name: Move to dist/
       run: |
         mkdir -p dist

.github/workflows/build-macos-wheels.yml

@@ -7,7 +7,7 @@ jobs:
     runs-on: macos-latest
     strategy:
       matrix:
-        python-version: [3.5, 3.6, 3.7, 3.8]
+        python-version: [3.5, 3.6, 3.7, 3.8, 3.9]
     steps:
     - uses: actions/checkout@v2
     - name: Set up Python ${{ matrix.python-version }}