add pip cache

Author: liangliangyy

.github/workflows/django.yml

@@ -47,6 +47,7 @@ jobs:
         uses: actions/setup-python@v1
         with:
           python-version: ${{ matrix.python-version }}
+          cache: 'pip'
       - name: Install Dependencies
         run: |
           python -m pip install --upgrade pip
@@ -98,6 +99,7 @@ jobs:
         uses: actions/setup-python@v1
         with:
           python-version: ${{ matrix.python-version }}
+          cache: 'pip'
       - name: Install Dependencies
         run: |
           python -m pip install --upgrade pip