added dev requirement file

Author: daniel-gray-tangent

.github/workflows/testing.yml

@@ -9,7 +9,7 @@ jobs:
       - name: Install Dependencies
         run: |
           python -m pip install --upgrade pip
-          pip install -r requirements.txt
+          pip install -r requirements-dev.txt
       - name: Run linting tools
         run: |
           cd app/