Add support for mutualTLS security scheme introduced in 3.1.0

[codechaotic]

Description

For enterprise applications one of the exciting new features with OAS 3.1 was the added support for mutual TLS authentication with APIs as a native part of OpenAPI. Can support for this security scheme be added when generating clients with @hey-api/openapi-ts?

ref: https://typespec.io/docs/libraries/http/authentication/#available-security-schemes

Currently generating a client with an OAS (3.1.0) including a security scheme of type "mutualTLS" results in an error message:

❗️ SDK warning: unsupported security scheme. Please open an issue if you'd like it added https://github.com/hey-api/openapi-ts/issues
{
  "type": "mutualTLS",
  "description": "Certificate signed requests"
}