Add development documentation for LimitedCapacity::Worker

In !42237 (merged) we've added the setup for running a limited number of jobs continuously. But we need to extend the development documentation for that.

The following discussion from !42237 (merged) should be addressed:

• @reprazent started a discussion: (+1 comment)

  This explanation is great, but we probably want to add this to doc/develoment/sidekiq_style_guide.md as well.

  Happy to have this in a follow up.