[DOC]: Make clear EA status in the README

[jarmak-nv]

How would you describe the priority of this documentation request

Significant improvement

Please provide a link or source to the relevant docs

https://github.com/NVIDIA/nv-ingest/blob/main/README.md

Describe the problems in the documentation

We should make it more clear that NV-Ingest is not yet GA and some challenges may be encountered during setup while we're in EA.

(Optional) Propose a correction or improvement

No response

[jarmak-nv]

I've added a note that NV-Ingest is Early Access in the "About" section. README update coming soon.