Caching dependencies

Prevents them from being reinstalled all the time

.github/workflows/python-package.yml

@@ -24,6 +24,13 @@ jobs:
       uses: actions/setup-python@v3
       with:
         python-version: ${{ matrix.python-version }}
+    - name: Cache pip
+      uses: actions/cache@v3
+        with:
+          path: ~/.cache/pip
+          key: ${{ runner.os }}-pip-${{ hashFiles('**/requirements.txt') }}
+          restore-keys: |
+            ${{ runner.os }}-pip-
     - name: Install dependencies
       run: |
         python -m pip install --upgrade pip