Add description for errors

[bevalorous]

A description field could be helpful for adding some additional information to the errors that doesn't necessarily end up going over the wire: what the error means, when and why it happens, how it can be handled or walked around, which actions may be performed to mitigate it, etc.

[github-actions]

Welcome to OpenRPC! Thank you for taking the time to create an issue. Please review the guidelines

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[BelfordZ]

Hey there

Good thinking. code, message and data are all fields which are returned as part of the json-rpc error response. As such, there is no where to add documentation that is to be consumed outside the request-response lifecycle.

In addition to description, I think we should also add a name field, which is essential for code generators to be able to produce typed errors.