Add conda cache for actions (#36)

Author: stefmolin

.github/workflows/env-checks.yml

@@ -57,6 +57,16 @@ jobs:
           else
               sed -i -e '/- python[>=]/d' environment.yml;
           fi;
+      
+      - name: Cache conda
+        uses: actions/cache@3624ceb22c1c5a301c8db4169662070a689d9ea8  # v4.1.1
+        env:
+          # Increase this value to reset cache if environment.yml has not changed
+          CACHE_NUMBER: 0
+        with:
+          path: ~/conda_pkgs_dir
+          key:
+            ${{ runner.os }}-${{ matrix.python-version }}-conda-${{ env.CACHE_NUMBER }}-${{ hashFiles('environment.yml') }}
 
       # create the conda env
       - uses: conda-incubator/setup-miniconda@a4260408e20b96e80095f42ff7f1a15b27dd94ca  # v3.0.4