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-301-nim.md

@@ -1,52 +1,40 @@
 ---
 id: 5900f4991000cf542c50ffab
-challengeType: 5
 title: 'Problem 301: Nim'
+challengeType: 5
 forumTopicId: 301955
 ---
 
-## Description
-<section id='description'>
+# --description--
 
 Nim is a game played with heaps of stones, where two players take it in turn to remove any number of stones from any heap until no stones remain.
 
 We'll consider the three-heap normal-play version of Nim, which works as follows:
 
-- At the start of the game there are three heaps of stones.
-- On his turn the player removes any positive number of stones from any single heap.
-- The first player unable to move (because no stones remain) loses.
+-   At the start of the game there are three heaps of stones.
+-   On his turn the player removes any positive number of stones from any single heap.
+-   The first player unable to move (because no stones remain) loses.
 
 If (n1,n2,n3) indicates a Nim position consisting of heaps of size n1, n2 and n3 then there is a simple function X(n1,n2,n3) — that you may look up or attempt to deduce for yourself — that returns: zero if, with perfect strategy, the player about to move will eventually lose; or non-zero if, with perfect strategy, the player about to move will eventually win. For example X(1,2,3) = 0 because, no matter what the current player does, his opponent can respond with a move that leaves two heaps of equal size, at which point every move by the current player can be mirrored by his opponent until no stones remain; so the current player loses. To illustrate:
 
-- current player moves to (1,2,1)
-- opponent moves to (1,0,1)
-- current player moves to (0,0,1)
-- opponent moves to (0,0,0), and so wins.
+-   current player moves to (1,2,1)
+-   opponent moves to (1,0,1)
+-   current player moves to (0,0,1)
+-   opponent moves to (0,0,0), and so wins.
 
-For how many positive integers n ≤ 230 does X(n,2n,3n) = 0 ?
-</section>
+For how many positive integers n ≤ 230 does X(n,2n,3n) = 0 ?
 
-## Instructions
-<section id='instructions'>
+# --hints--
 
-</section>
-
-## Tests
-<section id='tests'>
-
-```yml
-tests:
-  - text: <code>euler301()</code> should return 2178309.
-    testString: assert.strictEqual(euler301(), 2178309);
+`euler301()` should return 2178309.
 
+```js
+assert.strictEqual(euler301(), 2178309);
 ```
 
-</section>
+# --seed--
 
-## Challenge Seed
-<section id='challengeSeed'>
-
-<div id='js-seed'>
+## --seed-contents--
 
 ```js
 function euler301() {
@@ -57,17 +45,8 @@ function euler301() {
 euler301();
 ```
 
-</div>
-
-
-
-</section>
-
-## Solution
-<section id='solution'>
+# --solutions--
 
 ```js
 // solution required
 ```
-
-</section>