Update publish workflow to use new version file

Author: sgoodm

.github/workflows/build-and-publish.yml

@@ -24,7 +24,7 @@ jobs:
         pip install build
     - name: Get version
       run: |
-        cat setup.cfg | grep "version = " | awk '{print "VERSION="$(NF)}' >> $GITHUB_ENV
+        cat src/polygongrid/_version.py | awk '{print $(NF)}' >> $GITHUB_ENV
     - name: Build a binary wheel and a source tarball 🚧
       run: python -m build --sdist --wheel --outdir dist/ .
     - name: Validate release tag

src/polygongrid/_version.py

@@ -1 +1 @@
-__version__ = "0.1.0"
+__version__ = "0.1.0a1"