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-34-digit-factorials.md

@@ -1,12 +1,11 @@
 ---
 id: 5900f38e1000cf542c50fea1
-challengeType: 5
 title: 'Problem 34: Digit factorials'
+challengeType: 5
 forumTopicId: 301998
 ---
 
-## Description
-<section id='description'>
+# --description--
 
 145 is a curious number, as 1! + 4! + 5! = 1 + 24 + 120 = 145.
 
@@ -14,33 +13,23 @@ Find the numbers and the sum of the numbers which are equal to the sum of the fa
 
 **Note:** as 1! = 1 and 2! = 2 are not sums they are not included.
 
-</section>
+# --hints--
 
-## Instructions
-<section id='instructions'>
-
-</section>
-
-## Tests
-<section id='tests'>
-
-```yml
-tests:
-  - text: <code>digitFactorial()</code> should return an object.
-    testString: assert.typeOf(digitFactorial(), 'object');
-  - text: |
-      <code>digitFactorial()</code> should return { sum: 40730, numbers: [145, 40585] }.
-    testString: |
-      assert.deepEqual(digitFactorial(), { sum: 40730, numbers: [145, 40585] });
+`digitFactorial()` should return an object.
 
+```js
+assert.typeOf(digitFactorial(), 'object');
 ```
 
-</section>
+`digitFactorial()` should return { sum: 40730, numbers: [145, 40585] }.
 
-## Challenge Seed
-<section id='challengeSeed'>
+```js
+assert.deepEqual(digitFactorial(), { sum: 40730, numbers: [145, 40585] });
+```
 
-<div id='js-seed'>
+# --seed--
+
+## --seed-contents--
 
 ```js
 function digitFactorial() {
@@ -53,17 +42,8 @@ function digitFactorial() {
 digitFactorial();
 ```
 
-</div>
-
-
-
-</section>
-
-## Solution
-<section id='solution'>
+# --solutions--
 
 ```js
 // solution required
 ```
-
-</section>