Align Docs Is Allowed Example With Type Definition

[alexanderdavide]

Describe the issue/change

The docs show a wrong example of the isAllowed callback. It returns the inputObj if it passes the check or undefined. This actually works in JavaScript because of type coercion (IMO still a bad practice). However, in TypeScript the type definition enforces a boolean to be returned.

const MAX_VAL = 1400;
const withValueLimit = (inputObj) => {
  const { value } = inputObj;
  if (value < MAX_VAL) return inputObj;
};
<NumberFormat value={12} isAllowed={withValueLimit} />;

The type definition requires a boolean:

isAllowed?: (values: NumberFormatValues) => boolean;

Describe the changes proposed/implemented in this PR

Aligned the isAllowed example in the docs with the method's type definition.

Changes implemented

[nikhil-varma]

@alexanderdavide Merging this PR