Add CI workflow to run pytest

Run the test suite on push and pull request with the pandas, polars, db,
web, and bibliometrics extras so importorskip tests are not skipped.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Author: raffaelemancuso

.github/workflows/tests.yml

@@ -0,0 +1,23 @@
+name: tests
+
+on:
+  push:
+    branches: [master]
+  pull_request:
+
+jobs:
+  pytest:
+    name: Test suite
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Install uv
+        uses: astral-sh/setup-uv@v5
+
+      - name: Run pytest
+        run: >-
+          uv run
+          --extra dev --extra pandas --extra polars
+          --extra db --extra web --extra bibliometrics
+          pytest