Add error codes to all throws clauses

[LeaVerou]

Currently we throw errors with just an error message (example). This means that apps using Color.js only have two real options: catching all errors and just indicating that something went wrong, or passing the actual message string on to the user.

I think we can use the cause property to pass in more structured data, including an error code. If so, it would be good to do this across the codebase.