Add note about known limitation for CompareToWithoutComparable rule.
Add note about known limitation for CompareToWithoutComparable rule.

erdi/CodeNarc,CodeNarc/CodeNarc,darxriggs/CodeNarc,CodeNarc/CodeNarc,erdi/CodeNarc,erdi/CodeNarc,erdi/CodeNarc,darxriggs/CodeNarc