Update ci

Author: SaridakisStamatisChristos

.github/workflows/ci

@@ -1 +1,33 @@
+name: ci
+on:
+  push:
+  pull_request:
+
+jobs:
+  test:
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        python-version: ["3.10", "3.11", "3.12"]
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/setup-python@v5
+        with:
+          python-version: ${{ matrix.python-version }}
+      - uses: actions/cache@v4
+        with:
+          path: ~/.cache/pip
+          key: ${{ runner.os }}-pip-${{ hashFiles('pyproject.toml') }}
+          restore-keys: |
+            ${{ runner.os }}-pip-
+      - run: python -m pip install -U pip
+      - run: pip install -e ".[dev]"
+      - run: pytest -q --maxfail=1 --disable-warnings --cov=sudoku_dlx --cov-report=xml
+      - name: Upload coverage to Codecov
+        uses: codecov/codecov-action@v4
+        with:
+          token: ${{ secrets.CODECOV_TOKEN }}  # Not required for public repos
+          files: ./coverage.xml
+          flags: unittests
+          fail_ci_if_error: false