JSON Reactive RCP lite client

[streamich]

Create a light-weight brwoser-only client.

• Ships only client logic.
• Use DOM events instead of Observables.
• Use async iterables.
• Ships the simplest codec. Possibly hand-crafter compact codec.
• Ships with Base64 encoder/decoder for binary support.
• Uses fetch for request execution.
• Uses streaming fetch requests for reactive requests.