Add note about Result to `find_or_last` and `find_or_first` #1005

Job	Run time
doc	15s
check format	4s
check	39s
check (--no-default-features)	11s
miri	3m 1s
msrv	55s
check (--no-default-features --features use_alloc)	20s
check (--all-targets --all-features)	20s
semver-checks	13s
test	1m 3s
All checks succeeded	1s
	7m 2s

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