Stream API?

[vicary]

The whole Workerpool idea may be split up into two main parts:

1. A TaskEmitter which emit tasks as a ReadableSteam
2. A TaskExecutor acting as a WriteableStream which takes task objects as chunks.

Worker concurrency is essentially implemented as back pressure between the streams, we can even allow runner types to be added/removed on the fly.

Questions to be answered:

1. Does Deno streams support object mode?
2. What if TaskExecutor has other unknown data piped into it?