🧪 Fix codecov (#332)

.github/workflows/tests.yml

@@ -43,7 +43,7 @@ jobs:
     - name: Install dependencies
       run: |
         python -m pip install --upgrade pip
-        pip install .[testing,linkify]
+        pip install -e .[testing,linkify]
     - name: Run pytest
       run: |
         pytest tests/ --cov=markdown_it --cov-report=xml --cov-report=term-missing