Server-sent events client implementation about mappersmith HOT 1 OPEN

I think it looks very interesting and sounds like a fun project 👍
Since gateways are configurable I guess ideally it should be implemented in both HTTP and Fetch gateways, even though HTTP is the default it is not uncommon to override it to Fetch for node:

import forge, { configs } from 'mappersmith';
import fetchGateway from 'mappersmith/gateway/fetch';
import fetch from 'node-fetch';

configs.gateway = fetchGateway;
configs.fetch = fetch;
const client = forge({ ... })

from mappersmith.