n-api: add code parameter to error helpers

In support of the effort to add error codes to all errors
generated by Node.js, add an optional code parameter to the
helper functions used to throw/create errors in N-API.

PR-URL: https://github.com/nodejs/node/pull/13988
Fixes: https://github.com/nodejs/node/issues/13933
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>

lib/internal/errors.js

@@ -161,6 +161,8 @@ E('ERR_IPC_ONE_PIPE', 'Child process can have only one IPC pipe');
 E('ERR_IPC_SYNC_FORK', 'IPC cannot be used with synchronous forks');
 E('ERR_MISSING_ARGS', missingArgs);
 E('ERR_MULTIPLE_CALLBACK', 'Callback called multiple times');
+E('ERR_NAPI_CONS_FUNCTION', 'Constructor must be a function');
+E('ERR_NAPI_CONS_PROTOTYPE_OBJECT', 'Constructor.prototype must be an object');
 E('ERR_NO_CRYPTO', 'Node.js is not compiled with OpenSSL crypto support');
 E('ERR_PARSE_HISTORY_DATA', 'Could not parse history data in %s');
 E('ERR_SOCKET_ALREADY_BOUND', 'Socket is already bound');