Add cache to workflow

.github/workflows/pythonpackage.yml

@@ -12,27 +12,38 @@ jobs:
         python-version: ["3.8", "3.9", "3.10"]
     steps:
     - uses: actions/checkout@v3
+
     - name: Set up Python ${{ matrix.python-version }}
       uses: actions/setup-python@v4
       with:
         python-version: ${{ matrix.python-version }}
+
+    - uses: actions/cache@v2
+      with:
+        path: ~/.cache/pip
+        key: ${{ hashFiles('requirements.txt') }}-${{ hashFiles('requirements-testing.txt')}}-${{ hashFiles('tox.ini') }}
+
     - name: Install dependencies
       run: |
         python -m pip install --upgrade pip
         pip install -r requirements.txt -r requirements-testing.txt -c constraints-Django32.txt
+
     - name: Format style check with 'autopep8'
       run: |
         pip install autopep8
         autopep8 --exit-code --global-config .flake8 helpdesk
-    - name: Lint with flake8
+
+    - name: Lint with 'flake8'
       run: |
         pip install flake8
         # stop the build if there are Python syntax errors or undefined names
         # exit-zero treats all errors as warnings. The GitHub editor is 127 chars wide
         flake8 helpdesk --count --show-source --statistics --exit-zero --max-complexity=20
+
     - name: Sort style check with 'isort'
       run: |
         isort --line-length=120 --src helpdesk . --check
+
     - name: Test with pytest
       run: |
         pip install pytest