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-214-totient-chains.md

@@ -1,55 +1,35 @@
 ---
 id: 5900f4421000cf542c50ff55
-challengeType: 5
 title: 'Problem 214: Totient Chains'
+challengeType: 5
 forumTopicId: 301856
 ---
 
-## Description
-<section id='description'>
+# --description--
+
 Let φ be Euler's totient function, i.e. for a natural number n,
+
 φ(n) is the number of k, 1 ≤ k ≤ n, for which gcd(k,n) = 1.
 
-By iterating φ, each positive integer generates a decreasing chain of numbers ending in 1.
-E.g. if we start with 5 the sequence 5,4,2,1 is generated.
-Here is a listing of all chains with length 4:
+By iterating φ, each positive integer generates a decreasing chain of numbers ending in 1. E.g. if we start with 5 the sequence 5,4,2,1 is generated. Here is a listing of all chains with length 4:
 
-
-5,4,2,1
-7,6,2,1
-8,4,2,1
-9,6,2,1
-10,4,2,1
-12,4,2,1
-14,6,2,1
-18,6,2,1
+5,4,2,1 7,6,2,1 8,4,2,1 9,6,2,1 10,4,2,1 12,4,2,1 14,6,2,1 18,6,2,1
 
 Only two of these chains start with a prime, their sum is 12.
 
 What is the sum of all primes less than 40000000 which generate a chain of length 25?
-</section>
 
-## Instructions
-<section id='instructions'>
+# --hints--
 
-</section>
-
-## Tests
-<section id='tests'>
-
-```yml
-tests:
-  - text: <code>euler214()</code> should return 1677366278943.
-    testString: assert.strictEqual(euler214(), 1677366278943);
+`euler214()` should return 1677366278943.
 
+```js
+assert.strictEqual(euler214(), 1677366278943);
 ```
 
-</section>
+# --seed--
 
-## Challenge Seed
-<section id='challengeSeed'>
-
-<div id='js-seed'>
+## --seed-contents--
 
 ```js
 function euler214() {
@@ -60,17 +40,8 @@ function euler214() {
 euler214();
 ```
 
-</div>
-
-
-
-</section>
-
-## Solution
-<section id='solution'>
+# --solutions--
 
 ```js
 // solution required
 ```
-
-</section>