doc: Broken 'Getting Started Guide' link in root README

Please also confirm the following

• I have searched the main issue tracker of NeMo Guardrails repository and believe that this is not a duplicate

Issue Kind

Error in existing documentation

Existing Link

https://docs.nvidia.com/nemo/guardrails/getting-started

Description

The "Getting Started Guide" link in the Learn More section of the root README (https://github.com/NVIDIA-NeMo/Guardrails/blob/develop/README.md) is broken — it returns a 404.

$ curl -s -o /dev/null -w "%{http_code}" -L https://docs.nvidia.com/nemo/guardrails/getting-started
404

Suggested fix

The docs site has been reorganized: the URL scheme changed from getting-started to get-started. The link should be updated from

https://docs.nvidia.com/nemo/guardrails/getting-started

to

https://docs.nvidia.com/nemo/guardrails/get-started/installation-guide

(which resolves successfully) or another page under https://docs.nvidia.com/nemo/guardrails/get-started/ if the maintainers prefer a different landing page.