oversight: add security notice

oversight: add option to automatic prune done or failed processes

oversight: handle deletion of completed childprocs

oversight: prepare to rename default branch

oversight: upgrade minimum Go version

oversight/easy: update README.md

oversight: update Add() comment to account for func(context.Context)

oversight: deflake test mean to prove the clockwork will not panic

oversight: code grooming

oversight: fix panic on restart of canceled trees