Add test case for radios with number values

If the property values of the options are numbers, the return type should also be numbers.
Also adds type to the test case where the property values are strings.

types/storybook__addon-knobs/storybook__addon-knobs-tests.tsx

@@ -35,7 +35,8 @@ stories.add('with all knobs', () => {
   const selectedColor = color('Color', 'black');
   const favoriteNumber = number('Favorite Number', 42);
   const comfortTemp = number('Comfort Temp', 72, { range: true, min: 60, max: 90, step: 1 });
-  const radioStation = radios('Favorite Radio Station', { 1100: "1100", 2200: "2200", 3300: "3300" });
+  const radioStation: string = radios('Favorite Radio Station', { 1100: "1100", 2200: "2200", 3300: "3300" });
+  const luckyNumber: number = radios('Lucky Number', { 3: 3, 7: 7, 23: 23 });
   const textDecoration = select('Decoration', {
     None: 'none',
     Underline: 'underline',
@@ -77,6 +78,7 @@ stories.add('with all knobs', () => {
       <p>My favorite number is {favoriteNumber}.</p>
       <p>My most comfortable room temperature is {comfortTemp} degrees Fahrenheit.</p>
       <p>My favorite radio station is: {radioStation}</p>
+      <p>My lucky number is {luckyNumber}.</p>
     </div>
   );
 });