CodeUnits length function doc references itself and is wrong (#177)

* CodeUnits length function doc references itself and is wrong

* reference do Data.String.CodeUnits.length

* referencing Data.String.CodePoints.kength from Data.String.CodeUnits.length

Author: erykciepiela

src/Data/String/CodePoints.purs

@@ -207,7 +207,7 @@ uncons s = case CU.length s of
 -- | ```purescript
 -- | >>> length "b 𝐀𝐀 c 𝐀"
 -- | 8
--- | -- compare to Data.String:
+-- | -- compare to Data.String.CodeUnits:
 -- | >>> length "b 𝐀𝐀 c 𝐀"
 -- | 11
 -- | ```

src/Data/String/CodeUnits.purs

@@ -145,6 +145,10 @@ uncons s  = Just { head: U.charAt zero s, tail: drop one s }
 -- |
 -- | ```purescript
 -- | length "Hello World" == 11
+-- |
+-- | length "𝐀A" == 3
+-- | -- compare to Data.String.CodePoints:
+-- | length "𝐀A" == 2
 -- | ```
 -- |
 foreign import length :: String -> Int