Cherry pick docs: deepscaler guide on sidebar (401) into r0.2.1 (#402)

Signed-off-by: Terry Kong <terryk@nvidia.com>
Signed-off-by: NeMo Bot <nemo-bot@nvidia.com>
Co-authored-by: Terry Kong <terrycurtiskong@gmail.com>

Author: ko3n1g

docs/index.md

@@ -15,6 +15,7 @@ cluster.md
 :caption: 🚀 E2E Examples
 :hidden:
 
+guides/grpo-deepscaler.md
 guides/sft-openmathinstruct2.md
 ```