Added cache in github actions to speed up CI (#549)

Author: WisdomPill

.github/workflows/test.yml

@@ -15,6 +15,12 @@ jobs:
         uses: actions/setup-python@v2
         with:
           python-version: ${{ matrix.python-version }}
+      - uses: actions/cache@v2
+        with:
+          path: ~/.cache/pip
+          key: ${{ runner.os }}-pip-${{ matrix.python-version }}-lint-${{ hashFiles('./dev-requirements.txt') }}
+          restore-keys: |
+            ${{ runner.os }}-pip-${{ matrix.python-version }}-lint-
       - name: Install dependencies
         run: |
           pip install -U pip setuptools wheel
@@ -36,6 +42,12 @@ jobs:
         uses: actions/setup-python@v2
         with:
           python-version: ${{ matrix.python-version }}
+      - uses: actions/cache@v2
+        with:
+          path: ~/.cache/pip
+          key: ${{ runner.os }}-pip-${{ matrix.python-version }}-test-${{ hashFiles('./dev-requirements.txt') }}
+          restore-keys: |
+            ${{ runner.os }}-pip-${{ matrix.python-version }}-test-
       - name: Install dependencies
         run: |
           pip install -U pip setuptools wheel
@@ -58,6 +70,12 @@ jobs:
         uses: actions/setup-python@v2
         with:
           python-version: ${{ matrix.python-version }}
+      - uses: actions/cache@v2
+        with:
+          path: ~/.cache/pip
+          key: ${{ runner.os }}-pip-${{ matrix.python-version }}-${{ matrix.django-version }}-typecheck-${{ hashFiles('./dev-requirements.txt') }}
+          restore-keys: |
+            ${{ runner.os }}-pip-${{ matrix.python-version }}-${{ matrix.django-version }}-typecheck-
       - name: Install dependencies
         run: |
           pip install -U pip setuptools wheel