docs: queues and workers

[jtsextonMITRE]

Closes #1057

[jtsextonMITRE]

@jkglasbrenner Can you take a look since you're writing custom-workers? I didn't want to duplicate information too much but wasn't sure how much belonged in here vs. the custom workers how-to. In particular the dioptra-worker-v1 executable usage, not sure where we want to put that.

[colton-lapp]

As a non-technical Dioptra user, workers are quite confusing to me. I'm not really sure what the purpose of multiple workers are besides some are designed to work with GPUs and some are designed to work with CPUs. I left notes about the high-level questions I have about workers that would be useful for me to know in an explanation doc. I would consider adding content to answer these questions and de-emphasizing / reorganizing some of the more technical material which feels more appropriate in a reference page or a "How to build custom workers" page.

[keithmanville]

I would move what is a queue above what is a worker.
This would match the explainer title. I also think that Queue flows in to Worker based on how it's written.