feat(validatedtextinput): default field label to label defined in sch…

…ema if present (#85)

If the yup schema of a text field contains a `.label()` (needed for good error messages),
ValidatedTextInput will use it as a default for the `label` prop so the consumer doesn't have to
duplicate it.

src/components/ValidatedTextInput/ValidatedTextInput.tsx

@@ -32,7 +32,7 @@ interface IValidatedTextInputProps
 export const ValidatedTextInput: React.FunctionComponent<IValidatedTextInputProps> = ({
   field,
   component = TextInput,
-  label,
+  label = field.schema.describe().label,
   fieldId,
   isRequired,
   type = 'text',