add a paragraph to the landing page

[v0lkan]

This is a distilled version after parsing all the documentation and also correlating it with SPIFFE/SPIRE related published work too.

I might want to rephrase it a bie

“Aegis is a Kubernetes-native secure Key-Value store for secrets management. It provides a minimal and intuitive API, ensuring practical security without compromising user experience. Aegis is resilient and secure by default, storing sensitive data in memory and encrypting any data saved to disk. Endorsed by industry experts, Aegis is a ground-up re-imagination of secrets management, leveraging SPIFFE for authentication and providing a Kubernetes-native way to manage secrets end-to-end.”

[v0lkan]

Done.

[v0lkan]

Also updated docs/index.md