* Fix type on OOP as requested on issue #18091
fix:
numLegs: 2 to numLegs: 4
on challenge:
Remember to Set the Constructor Property when Changing the Prototype
* Update remember-to-set-the-constructor-property-when-changing-the-prototype.english.md
* User Flow: Information, Articles, Youtube update
Explanation on what is User Flow with youtube videos and articles for reference and/or resource.
* Update of UX Design article
Update the article with more information and more links to articles and books.
* Product Design: Info, Articles, Youtube update
Explanation on what is Product Design with youtube videos and articles for reference and/or resource.
* Update description of Retina Display
As reported in issue #18129, there is a lack of explanation on what a retina display is and some users find it difficult to understand what they are doing exactly, so I added a short explanation on what a High-Resolution Display is and what a Retina Display is.