chore: add pytest-cov and CI workflow

Add GitHub Actions workflow for running tests with coverage on Python 3.8 and 3.11.

Configure pytest-cov, coverage thresholds and expand testpaths in pyproject.toml.

Update .gitignore for .ruff_cache, .mypy_cache, *.egg-info and .coverage.

.github/workflows/tests.yml

@@ -0,0 +1,36 @@
+name: Tests
+
+on:
+  push:
+    branches: [develop, master]
+  pull_request:
+    branches: [develop, master]
+
+jobs:
+  test:
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        python-version: ["3.8", "3.11"]
+
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Set up Python
+        uses: actions/setup-python@v5
+        with:
+          python-version: ${{ matrix.python-version }}
+
+      - name: Install dependencies
+        run: |
+          python -m pip install --upgrade pip
+          pip install -e ".[dev]"
+
+      - name: Run tests with coverage
+        run: pytest --cov=kiauh --cov-report=xml --cov-report=term
+
+      - name: Upload coverage
+        uses: actions/upload-artifact@v4
+        with:
+          name: coverage-${{ matrix.python-version }}
+          path: coverage.xml