👷 add model and package cache

.github/workflows/pytest.yml

@@ -14,6 +14,16 @@ jobs:
         uses: actions/setup-python@v2
         with:
           python-version: ${{ matrix.python-version }}
+      - name: Cache spleeter models
+        uses: actions/cache@v2
+        env:
+          cache-name: cache-spleeter-model
+        with:
+          path: pretrained_models
+          key: models-${{ hashFiles('spleeter/model/__init__.py') }}
+          restore-keys: |
+            models-${{ hashFiles('spleeter/model/__init__.py') }}
+            models-
       - name: Install dependencies
         run: |
           sudo apt-get update && sudo apt-get install -y ffmpeg