Added black & flake8 to Github actions

Author: seanlaw

.github/workflows/github-actions.yml

@@ -17,3 +17,7 @@ jobs:
         run: python -c "import sys; print(sys.version)"
       - name: Install STUMPY And Other Dependencies
         run: pip install --editable .[ci]
+      - name: Run Black
+        run: black --check --diff ./
+      - name: Run Flake8
+        run: flake8 ./