Add: [Actions] check for flake8 and black issues

.github/workflows/testing.yml

@@ -13,7 +13,32 @@ jobs:
     steps:
     - name: Checkout
       uses: actions/checkout@v2
-    - name: Checkout submodules
-      uses: openttd/actions/checkout@v1
     - name: Build
       run: docker build .
+
+  flake8:
+    name: Flake8
+    runs-on: ubuntu-latest
+    steps:
+    - name: Checkout
+      uses: actions/checkout@v2
+    - name: Flake8
+      uses: TrueBrain/actions-flake8@master
+      with:
+        path: dorpsgek
+
+  black:
+    name: Black
+    runs-on: ubuntu-latest
+    steps:
+    - name: Checkout
+      uses: actions/checkout@v2
+    - name: Set up Python 3.7
+      uses: actions/setup-python@v1
+      with:
+        python-version: 3.7
+    - name: Black
+      run: |
+        python -m pip install --upgrade pip
+        pip install black
+        black -l 120 --check dorpsgek