Add note about Result to `find_or_last` and `find_or_first` #1004

Job	Run time
check format	4s
doc	7s
check	8s
check (--no-default-features)	8s
miri	2m 55s
semver-checks	10s
check (--no-default-features --features use_alloc)	12s
test	53s
check (--all-targets --all-features)	20s
msrv	56s
All checks succeeded	1s
	5m 54s

Provide feedback