feat(isNumber): Add module isNumber

Checks if a value is a number

src/__tests__/isNumber.js

@@ -0,0 +1,12 @@
+import isNumber from '../isNumber';
+
+test('Core.isNumber', () => {
+  expect(isNumber(1)).toBeTruthy();
+  expect(isNumber({})).toBeFalsy();
+  expect(isNumber({ foo: 'bar' })).toBeFalsy();
+  expect(isNumber(() => null)).toBeFalsy();
+  expect(isNumber([])).toBeFalsy();
+  expect(isNumber('a')).toBeFalsy();
+  expect(isNumber(null)).toBeFalsy();
+  expect(isNumber(undefined)).toBeFalsy();
+});

src/index.js

@@ -12,6 +12,7 @@ import is from './is';
 import isArray from './isArray';
 import isFunction from './isFunction';
 import isNil from './isNil';
+import isNumber from './isNumber';
 import isObject from './isObject';
 import last from './last';
 import map from './map';
@@ -38,6 +39,7 @@ export {
   isArray,
   isFunction,
   isNil,
+  isNumber,
   isObject,
   last,
   map,

src/isNumber.js

@@ -0,0 +1,3 @@
+import is from './is';
+
+export default x => is('number', x);