Incomplete Rt/Rtx monorepo

### Desire

Bringing rtx into rt to create a [workspace](https://docs.deno.com/runtime/fundamentals/workspaces/)-based monorepo would improve maintainability of both packages.

### Success stories

- https://github.com/FartLabs/ht/issues/11 consolidates packages `@fartlabs/ht` and `@fartlabs/htx` and improves convenience of maintainability.