CI: name doc artifacts after their respective packages

.github/workflows/check-docs.yml

@@ -39,8 +39,13 @@ jobs:
       - name: Build documentation packages
         run: nix build .#${{ matrix.package }} --print-build-logs
 
+      - name: Get current date
+        id: get-date
+        # output format: 2023-12-22-120000
+        run: echo "date=$(date +'%Y-%m-%d-%H%M%S')" >> ${GITHUB_OUTPUT}
+
       - name: Upload doc artifacts
         uses: actions/upload-artifact@v4
         with:
-          name: doc
+          name: "${{ matrix.package }}"
           path: result/share/doc/neovim-flake/