[Doc] Add smal table for GEMM backends (#20213)

docs/README.md

@@ -9,11 +9,18 @@ Most documentation files are located under the `docs/` folder.
 
 ### Install Dependency
 
+**Linux:**
 ```bash
 apt-get update && apt-get install -y pandoc parallel retry
 pip install -r requirements.txt
 ```
 
+**macOS:**
+```bash
+brew install pandoc parallel retry
+pip install -r requirements.txt
+```
+
 ### Update Documentation
 
 Update your Jupyter notebooks in the appropriate subdirectories under `docs/`. If you add new files, remember to update `index.rst` (or relevant `.rst` files) accordingly.