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-330-eulers-number.md

@@ -1,55 +1,41 @@
 ---
 id: 5900f4b71000cf542c50ffc9
-challengeType: 5
 title: 'Problem 330: Euler''s Number'
+challengeType: 5
 forumTopicId: 301988
 ---
 
-## Description
-<section id='description'>
+# --description--
 
 An infinite sequence of real numbers a(n) is defined for all integers n as follows:
+
 <!-- TODO Use MathJax and re-write from projecteuler.net -->
-For example,a(0) = 11! + 12! + 13! + ... = e − 1
-a(1) = e − 11! + 12! + 13! + ... = 2e − 3
-a(2) = 2e − 31! + e − 12! + 13! + ... = 72 e − 6
+
+For example,a(0) = 11! + 12! + 13! + ... = e − 1 a(1) = e − 11! + 12! + 13! + ... = 2e − 3 a(2) = 2e − 31! + e − 12! + 13! + ... = 72 e − 6
 
 with e = 2.7182818... being Euler's constant.
 
-
 It can be shown that a(n) is of the form
 
-A(n) e + B(n)n!
-for integers A(n) and B(n).
+A(n) e + B(n)n! for integers A(n) and B(n).
 
 For example a(10) =
 
 328161643 e − 65269448610!.
 
 Find A(109) + B(109) and give your answer mod 77 777 777.
-</section>
 
-## Instructions
-<section id='instructions'>
+# --hints--
 
-</section>
-
-## Tests
-<section id='tests'>
-
-```yml
-tests:
-  - text: <code>euler330()</code> should return 15955822.
-    testString: assert.strictEqual(euler330(), 15955822);
+`euler330()` should return 15955822.
 
+```js
+assert.strictEqual(euler330(), 15955822);
 ```
 
-</section>
+# --seed--
 
-## Challenge Seed
-<section id='challengeSeed'>
-
-<div id='js-seed'>
+## --seed-contents--
 
 ```js
 function euler330() {
@@ -60,17 +46,8 @@ function euler330() {
 euler330();
 ```
 
-</div>
-
-
-
-</section>
-
-## Solution
-<section id='solution'>
+# --solutions--
 
 ```js
 // solution required
 ```
-
-</section>