doc: Add 'don't ignore errors' section to domain
doc: Add 'don't ignore errors' section to domain

Also, an example program of using cluster and domain to handle errors
safely, with zero downtime, using process isolation.

dreamllq/node,dreamllq/node,dreamllq/node,dreamllq/node,dreamllq/node,dreamllq/node,dreamllq/node,dreamllq/node,dreamllq/node