Add note about Result to `find_or_last` and `find_or_first` #1000

Job	Run time
check format	14s
check	9s
miri	2m 58s
check (--no-default-features)	8s
msrv	53s
check (--no-default-features --features use_alloc)	10s
doc	17s
semver-checks	8s
check (--all-targets --all-features)	23s
test	51s
All checks succeeded	0s
	6m 11s

Provide feedback