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-202-laserbeam.md

@@ -1,45 +1,31 @@
 ---
 id: 5900f4371000cf542c50ff49
-challengeType: 5
 title: 'Problem 202: Laserbeam'
+challengeType: 5
 forumTopicId: 301843
 ---
 
-## Description
-<section id='description'>
+# --description--
+
 Three mirrors are arranged in the shape of an equilateral triangle, with their reflective surfaces pointing inwards. There is an infinitesimal gap at each vertex of the triangle through which a laser beam may pass.
 
 Label the vertices A, B and C. There are 2 ways in which a laser beam may enter vertex C, bounce off 11 surfaces, then exit through the same vertex: one way is shown below; the other is the reverse of that.
 
-
-
-
 There are 80840 ways in which a laser beam may enter vertex C, bounce off 1000001 surfaces, then exit through the same vertex.
 
 In how many ways can a laser beam enter at vertex C, bounce off 12017639147 surfaces, then exit through the same vertex?
-</section>
 
-## Instructions
-<section id='instructions'>
+# --hints--
 
-</section>
-
-## Tests
-<section id='tests'>
-
-```yml
-tests:
-  - text: <code>euler202()</code> should return 1209002624.
-    testString: assert.strictEqual(euler202(), 1209002624);
+`euler202()` should return 1209002624.
 
+```js
+assert.strictEqual(euler202(), 1209002624);
 ```
 
-</section>
+# --seed--
 
-## Challenge Seed
-<section id='challengeSeed'>
-
-<div id='js-seed'>
+## --seed-contents--
 
 ```js
 function euler202() {
@@ -50,17 +36,8 @@ function euler202() {
 euler202();
 ```
 
-</div>
-
-
-
-</section>
-
-## Solution
-<section id='solution'>
+# --solutions--
 
 ```js
 // solution required
 ```
-
-</section>