Feat: add new Markdown parser (#39800)

and change all the challenges to new `md` format.

curriculum/challenges/english/10-coding-interview-prep/project-euler/problem-313-sliding-game.md

@@ -1,46 +1,31 @@
 ---
 id: 5900f4a61000cf542c50ffb8
-challengeType: 5
 title: 'Problem 313: Sliding game'
+challengeType: 5
 forumTopicId: 301969
 ---
 
-## Description
-<section id='description'>
+# --description--
+
 In a sliding game a counter may slide horizontally or vertically into an empty space. The objective of the game is to move the red counter from the top left corner of a grid to the bottom right corner; the space always starts in the bottom right corner. For example, the following sequence of pictures show how the game can be completed in five moves on a 2 by 2 grid.
 
-
-
 Let S(m,n) represent the minimum number of moves to complete the game on an m by n grid. For example, it can be verified that S(5,4) = 25.
 
+There are exactly 5482 grids for which S(m,n) = p2, where p &lt; 100 is prime.
 
+How many grids does S(m,n) = p2, where p &lt; 106 is prime?
 
-There are exactly 5482 grids for which S(m,n) = p2, where p < 100 is prime.
+# --hints--
 
-How many grids does S(m,n) = p2, where p < 106 is prime?
-</section>
-
-## Instructions
-<section id='instructions'>
-
-</section>
-
-## Tests
-<section id='tests'>
-
-```yml
-tests:
-  - text: <code>euler313()</code> should return 2057774861813004.
-    testString: assert.strictEqual(euler313(), 2057774861813004);
+`euler313()` should return 2057774861813004.
 
+```js
+assert.strictEqual(euler313(), 2057774861813004);
 ```
 
-</section>
+# --seed--
 
-## Challenge Seed
-<section id='challengeSeed'>
-
-<div id='js-seed'>
+## --seed-contents--
 
 ```js
 function euler313() {
@@ -51,17 +36,8 @@ function euler313() {
 euler313();
 ```
 
-</div>
-
-
-
-</section>
-
-## Solution
-<section id='solution'>
+# --solutions--
 
 ```js
 // solution required
 ```
-
-</section>