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-281-pizza-toppings.md

@@ -1,44 +1,31 @@
 ---
 id: 5900f4861000cf542c50ff98
-challengeType: 5
 title: 'Problem 281: Pizza Toppings'
+challengeType: 5
 forumTopicId: 301932
 ---
 
-## Description
-<section id='description'>
+# --description--
+
 You are given a pizza (perfect circle) that has been cut into m·n equal pieces and you want to have exactly one topping on each slice.
 
-Let f(m,n) denote the number of ways you can have toppings on the pizza with m different toppings (m ≥ 2), using each topping on exactly n slices (n ≥ 1). Reflections are considered distinct, rotations are not.
+Let f(m,n) denote the number of ways you can have toppings on the pizza with m different toppings (m ≥ 2), using each topping on exactly n slices (n ≥ 1). Reflections are considered distinct, rotations are not.
 
-Thus, for instance, f(2,1) = 1, f(2,2) = f(3,1) = 2 and f(3,2) = 16. f(3,2) is shown below:
+Thus, for instance, f(2,1) = 1, f(2,2) = f(3,1) = 2 and f(3,2) = 16. f(3,2) is shown below:
 
+Find the sum of all f(m,n) such that f(m,n) ≤ 1015.
 
+# --hints--
 
-Find the sum of all f(m,n) such that f(m,n) ≤ 1015.
-</section>
-
-## Instructions
-<section id='instructions'>
-
-</section>
-
-## Tests
-<section id='tests'>
-
-```yml
-tests:
-  - text: <code>euler281()</code> should return 1485776387445623.
-    testString: assert.strictEqual(euler281(), 1485776387445623);
+`euler281()` should return 1485776387445623.
 
+```js
+assert.strictEqual(euler281(), 1485776387445623);
 ```
 
-</section>
+# --seed--
 
-## Challenge Seed
-<section id='challengeSeed'>
-
-<div id='js-seed'>
+## --seed-contents--
 
 ```js
 function euler281() {
@@ -49,17 +36,8 @@ function euler281() {
 euler281();
 ```
 
-</div>
-
-
-
-</section>
-
-## Solution
-<section id='solution'>
+# --solutions--
 
 ```js
 // solution required
 ```
-
-</section>