Upload codecove XML report

Author: dannyadair

.github/workflows/tests.yaml

@@ -23,5 +23,12 @@ jobs:
           echo "VIRTUAL_ENV=$PWD/.venv" >> $GITHUB_ENV
           echo "$PWD/.venv/bin" >> $GITHUB_PATH
           uv sync --dev
-      - name: Run tests with pytest
-        run: pytest
+      - name: Run tests with pytest and collect coverage
+        run: pytest --cov=pdfbaker --cov-report=xml
+      - name: Upload coverage to Codecov
+        uses: codecov/codecov-action@v3
+        with:
+          file: coverage.xml
+          name: pytest
+          flags: unittests
+          slug: pythonnz/pdfbaker