Add "Knights of the Flexbox table" game (#5489)

Welcome to the Knights of the Flexbox table. A game where you can help Sir Frederic Flexbox and his friends to uncover the treasures hidden in the Tailwind CSS dungeons.
You can navigate the knight through the dungeon by changing his position within the dungeon using Flexbox and Tailwind CSS.

more/free-programming-interactive-tutorials-en.md

@@ -147,6 +147,7 @@
 * [FreeCodeCamp: Responsive Web Design Course](https://www.freecodecamp.org/learn/responsive-web-design/basic-html-and-html5/)
 * [Grid Garden](https://cssgridgarden.com)
 * [HTML Tutorial](https://www.w3schools.com/html/) - W3Schools
+* [Knights of the Flexbox Table](https://knightsoftheflexboxtable.com)
 * [Learn by doing beginner projects](https://dash.generalassemb.ly)
 * [Learn HTML & CSS interactively](https://www.codecademy.com/learn/web)
 * [Prototyping a professional website](https://www.codecademy.com/learn/make-a-website)