add note about responsive design, close #237

Author: bahmutov

README.md

@@ -260,7 +260,7 @@ If you are using [plugins/cra-v3](plugins/cra-v3) it instruments the code on the
 
 You can use any Cypress [Visual Testing plugin](https://on.cypress.io/plugins#visual-testing) to perform [visual testing](https://on.cypress.io/visual-testing) from the component tests. This repo has several example projects, see [visual-sudoku](examples/visual-sudoku), [visual-testing-with-percy](examples/visual-testing-with-percy), [visual-testing-with-happo](examples/visual-testing-with-happo), and [visual-testing-with-applitools](examples/visual-testing-with-applitools).
 
-For a larger Do-It-Yourself example with an hour long list of explanation videos, see [bahmutov/sudoku](https://github.com/bahmutov/sudoku) repository.
+For a larger Do-It-Yourself example with an hour long list of explanation videos, see [bahmutov/sudoku](https://github.com/bahmutov/sudoku) repository. There you can also find an example of testing responsive design, as shown in this [video](https://youtu.be/j8yV3uKIJO0).
 
 ## Common problems