adds ci workflow for automated testing

Sets up a GitHub Actions workflow to run tests
on push and pull requests to the main branch.

The workflow uses multiple Python versions to
ensure compatibility across different environments.

Author: hellobertrand

.github/workflows/test.yml

@@ -0,0 +1,24 @@
+name: Tests
+
+on:
+  push:
+    branches: [main]
+  pull_request:
+    branches: [main]
+
+jobs:
+  test:
+    runs-on: ubuntu-latest
+
+    strategy:
+      matrix:
+        python-version: ["3.9", "3.10", "3.11"]
+
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/setup-python@v4
+        with:
+          python-version: ${{ matrix.python-version }}
+
+      - run: python -m pip install --upgrade pip
+      - run: python -m unittest discover -s src/screenshotmax/tests -p 'test_*.py'

src/screenshotmax/tests/__init__.py

@@ -0,0 +1,2 @@
+# This file marks the tests directory as a Python package, enabling relative imports
+