Include an example of the LOOKUP function in the Ref Guide

Once again I confused myself while trying to use the LOOKUP function. The first three arguments are all quoted strings. A simple example might help demonstrate this to the reader. I believe this may work as it follows the descriptive text.

SELECT LOOKUP('ModelName.StatePostalCodes', 'StateDisplayName', 'PostalCode', Table.WhatStateMatchesThisPostalCode) AS LookedUpStateName FROM Table