publish release candidates in PyPI

.github/workflows/ci.yml

@@ -51,7 +51,7 @@ jobs:
         if: github.event_name == 'push' && startsWith(github.event.ref, 'refs/tags')
         id: check-tag
         run: |
-          if [[ ${{ github.event.ref }} =~ ^refs/tags/[0-9]+\.[0-9]+\.[0-9]+$ ]]; then
+          if [[ ${{ github.event.ref }} =~ ^refs/tags/[0-9]+\.[0-9]+\.[0-9]+(rc[0-9]*)?$ ]]; then
               echo ::set-output name=match::true
           fi
       - name: Set up Python 3.7