docs(oneOf): Add contains flag to oneOf documentation

Author: Víctor Oliva

lib/chai/core/assertions.js

@@ -3117,6 +3117,14 @@ module.exports = function (chai, _) {
    *     expect(1).to.equal(1); // Recommended
    *     expect(1).to.not.be.oneOf([2, 3, 4]); // Not recommended
    *
+   * It can also be chained with `.contain` or `.include`, which will work with
+   * both arrays and strings:
+   * 
+   *     expect('Today is sunny').to.contain.oneOf(['sunny', 'cloudy'])
+   *     expect('Today is rainy').to.not.contain.oneOf(['sunny', 'cloudy'])
+   *     expect([1,2,3]).to.contain.oneOf([3,4,5])
+   *     expect([1,2,3]).to.not.contain.oneOf([4,5,6])
+   * 
    * `.oneOf` accepts an optional `msg` argument which is a custom error message
    * to show when the assertion fails. The message can also be given as the
    * second argument to `expect`.