Cache ./target in CI between tox runs

Author: hombit

.github/workflows/test.yml

@@ -47,6 +47,10 @@ jobs:
         uses: actions/setup-python@v5
         with:
           python-version: "3.${{ matrix.python_minor }}"
+      - uses: Swatinem/rust-cache@v2
+        with:
+          shared-key: "${{ runner.os }}_stable-rust_tox-py3${{ matrix.python_minor }}"
+          workspaces: "light-curve"
       - name: Install tox
         run: pip install tox
       - name: Run Python tests