Add disclaimer

Author: mtmk

README.md

@@ -6,6 +6,26 @@
 
 This is a .NET implementation of the JWT library for the NATS ecosystem.
 
+> [!NOTE]
+> ### Very Important Disclaimer
+>
+> This repository provides an API to build NATS JWTs using .NET. However, at
+> this time it is _not_ a supported API. Use at your own risk.
+> 
+> One important take away from this project is that the purpose of the library is
+> for building JWTs, not to validate them exhaustively. This means that tokens
+> generated by this library are expected to be validated by a process that uses
+> the [NATS JWT Go library](github.com/nats-io/jwt). As that library is the one
+> used by:
+> 
+> - [nats-server](github.com/nats-io/nats-server),
+> - [nats-account-server](github.com/nats-io/nats-account-server)
+> - [nsc](github.com/nats-io/nsc)
+> 
+> Under that context, ultimate validity of the JWT is delegated to tools or
+> servers that use the [NATS JWT Go library](github.com/nats-io/jwt). Use of this
+> library implies an agreement with the above disclaimer.
+
 ## TODO
 
 - [x] Add public API analyzer