Cache nix

.forgejo/install-emacs/action.yml

@@ -7,7 +7,21 @@ inputs:
 runs:
   using: 'composite'
   steps:
+    - name: Restore cached version
+      id: cache-restore
+      uses: https://code.forgejo.org/actions/cache/restore@v4
+      with:
+        path: |
+          /nix/store
+        key: ${{ inputs.version }}-${{ hashFiles('flake.lock') }}
     - run: ${{ github.action_path }}/install.sh
       shell: bash
       env:
         INPUT_VERSION: ${{ inputs.version }}
+    - name: Cache version
+      id: cache-put
+      uses: https://code.forgejo.org/actions/cache/save@v4
+      with:
+        path: |
+          /nix/store
+        key: ${{ inputs.version }}-${{ hashFiles('flake.lock') }}