Open-sourced NATS JetStream and Kubernetes adapters for Casbin

Hey guys,

Two weeks ago, I discovered the Casbin project, and I think it’s really great.
I've also presented it to a colleague of mine, and they share my opinion and appreciate its simplicity.
Thank you for the great work!

Anyway, I would like to give something back to the open-source community, and I’ve open-sourced two adapters:

• Adapter for NATS JetStream: https://github.com/grepplabs/casbin-jetstream
• Adapter + Informer for Kubernetes: https://github.com/grepplabs/casbin-kube

Any feedback is appreciated!

@michal_60030 they look great! Can you add them to the docs site's adapter list: https://casbin.org/docs/adapters ? (via making Pull Request)

@hsluoyz I've just created a Pull Request https://github.com/casbin/casbin-website-v2/pull/302
Semantic PR check is failing, but I don't know how to fix it

PR already merged, thanks for the contribution!

ty bro