CI(docs): Use mold linker (#5642)

Author: echoix

.github/workflows/documentation.yml

@@ -70,6 +70,8 @@ jobs:
           pip install -r grass/.github/workflows/python_requirements.txt
           pip install -r grass-addons/.github/workflows/requirements.txt
 
+      - uses: rui314/setup-mold@e16410e7f8d9e167b74ad5697a9089a35126eb50 # v1
+
       - name: Create installation directory
         run: |
           mkdir "$HOME/install"