Add contributing/getting help to readme
Allow disabling/changing autostart/autostop behaviour
Import io_read and io_write from fiber_scheduler
Work around race condition

Only seems to come up on Ruby 3.0, but safe to do in any case
Do not resume dead Fibers

They may be dead due to a Fiber#raise, especially due to Timeout
Use EM.defer for ProcessWait fallback
Run when there is any EM work left