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-432-totient-sum.md

@@ -1,41 +1,29 @@
 ---
 id: 5900f51e1000cf542c510030
-challengeType: 5
 title: 'Problem 432: Totient sum'
+challengeType: 5
 forumTopicId: 302103
 ---
 
-## Description
-<section id='description'>
+# --description--
+
 Let S(n,m) = ∑φ(n × i) for 1 ≤ i ≤ m. (φ is Euler's totient function)
+
 You are given that S(510510,106 )= 45480596821125120.
 
+Find S(510510,1011). Give the last 9 digits of your answer.
 
-Find S(510510,1011).
-Give the last 9 digits of your answer.
-</section>
+# --hints--
 
-## Instructions
-<section id='instructions'>
-
-</section>
-
-## Tests
-<section id='tests'>
-
-```yml
-tests:
-  - text: <code>euler432()</code> should return 754862080.
-    testString: assert.strictEqual(euler432(), 754862080);
+`euler432()` should return 754862080.
 
+```js
+assert.strictEqual(euler432(), 754862080);
 ```
 
-</section>
+# --seed--
 
-## Challenge Seed
-<section id='challengeSeed'>
-
-<div id='js-seed'>
+## --seed-contents--
 
 ```js
 function euler432() {
@@ -46,17 +34,8 @@ function euler432() {
 euler432();
 ```
 
-</div>
-
-
-
-</section>
-
-## Solution
-<section id='solution'>
+# --solutions--
 
 ```js
 // solution required
 ```
-
-</section>