chore: Add test coverage workflow (#218)

Closes #216

.github/workflows/coverage.yml

@@ -0,0 +1,24 @@
+name: Coverage
+on: [push, pull_request]
+jobs:
+  coverage:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v3
+      - name: Set up Python
+        uses: actions/setup-python@v4
+        with:
+          python-version: '3.10'
+      - name: Install dependencies
+        run: |
+          python -m pip install --upgrade pip
+          pip install pytest pytest-cov
+          pip install -e .
+      - name: Run tests with coverage
+        run: |
+          pytest --cov=tirith tests/
+      - name: Upload coverage report
+        uses: actions/upload-artifact@v3
+        with:
+          name: coverage-report
+          path: coverage.xml

README.md

@@ -3,6 +3,7 @@
 [![Quality Gate Status](https://sonarcloud.io/api/project_badges/measure?project=StackGuardian_policy-framework&metric=alert_status&token=4a4d06e73940505edb7fc9d27a7f03b35fbbf23d)](https://sonarcloud.io/summary/new_code?id=StackGuardian_policy-framework)
 [![Maintainability Rating](https://sonarcloud.io/api/project_badges/measure?project=StackGuardian_policy-framework&metric=sqale_rating&token=4a4d06e73940505edb7fc9d27a7f03b35fbbf23d)](https://sonarcloud.io/summary/new_code?id=StackGuardian_policy-framework)
 [![Slack](https://img.shields.io/badge/Slack-4A154B?style=for-the-badge&logo=slack&logoColor=white)](https://join.slack.com/t/stackguardian-ol78820/shared_invite/zt-2ksag36j9-OjmXqQmyXudgYrV6FmesIQ)
+[![codecov](https://codecov.io/gh/StackGuardian/tirith/branch/main/graph/badge.svg)](https://codecov.io/gh/StackGuardian/tirith)
 
 # Tirith (StackGuardian Policy Framework)