Need maturin in build.

Author: cottrell

.github/workflows/CI.yml

@@ -94,6 +94,8 @@ jobs:
           cp wheels-ubuntu/*.tar.gz dist/
           cp wheels-windows/*.whl dist/
           cp wheels-macos/*.whl dist/
+      - name: Install maturin
+        run: pip install maturin
       - name: Publish to PyPI
         uses: messense/maturin-action@v1
         env: