Add steps to build project in publishing workflow

Workflow adjustments are drawn from parts of a blog post.

References:
* https://johnfraney.ca/blog/how-to-publish-a-python-package-with-poetry-and-github-actions/

Disclaimer:
Participation by NIST in the creation of the documentation of mentioned
software is not intended to imply a recommendation or endorsement by the
National Institute of Standards and Technology, nor is it intended to
imply that any specific software is necessarily the best available for
the purpose.

Signed-off-by: Alex Nelson <alexander.nelson@nist.gov>

Author: ajnelson-nist

.github/workflows/publish.yml

@@ -31,5 +31,21 @@ jobs:
       # https://docs.pypi.org/trusted-publishers/using-a-publisher/
       id-token: write
     steps:
+      - name: Checkout Repository
+        uses: actions/checkout@v4
+
+      - name: Set up oldest tested Python
+        uses: actions/setup-python@v5
+        with:
+          python-version: "3.9"
+
+      - name: Install Dependencies
+        run: |
+          pip -q install poetry
+          poetry install
+
+      - name: Build Package
+        run: poetry build
+
       - name: Push to PyPi
         uses: pypa/gh-action-pypi-publish@release/v1