added flake8 to actions yml

.github/workflows/python-package.yml

@@ -25,6 +25,7 @@ jobs:
     - name: Install dependencies
       run: |
         python -m pip install --upgrade pip setuptools
+        pip install flake8
         if [ -f requirements.txt ]; then pip install -r requirements.txt; fi
         
     - name: Install Budgitree