Example
var { isEmail } = require("./index");
isEmail("") --> false, empty
isEmail("123@gmail.com") --> false, begin by number
isEmail(undefined) --> false
isEmail(null) --> false
isEmail("123456") --> false
isEmail("asnak") --> false
isEmail("!#@$FDS$") --> false
isEmail("abc0011@gmail.com") --> true