Fix type signature of jsonParser in quick start

Author: thomashoneyman

README.md

@@ -65,13 +65,13 @@ someObject =
     )
 ```
 
-Finally, you can parse JSON from a string using the `jsonParser` function. However, this isn't guaranteed to produce a correct value, so it returns a `Maybe` value.
+Finally, you can parse JSON from a string using the `jsonParser` function. However, this isn't guaranteed to produce a correct value, so it returns an `Either` value, where a parsing error is represented with `Left` containing an error message.
 
 ```purs
 import Data.Argonaut.Core (jsonParser)
 import Data.Maybe (Maybe(..))
 
-someObject :: Maybe Json
+someObject :: Either String Json
 someObject = jsonParser
   """
   { people: [{ name: "John" }, { name: "Jane" }] };