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-228-minkowski-sums.md

@@ -1,21 +1,21 @@
 ---
 id: 5900f4511000cf542c50ff63
-challengeType: 5
 title: 'Problem 228: Minkowski Sums'
+challengeType: 5
 forumTopicId: 301871
 ---
 
-## Description
-<section id='description'>
+# --description--
 
 <!-- TODO Use MathJax and re-write from projecteuler.net -->
+
 Let Sn be the regular n-sided polygon – or shape – whose vertices
 
-vk (k = 1,2,…,n) have coordinates:
+vk (k = 1,2,…,n) have coordinates:
 
-xk = cos( 2k-1/n ×180° )
+xk = cos( 2k-1/n ×180° )
 
-yk  =  sin( 2k-1/n ×180° )
+yk = sin( 2k-1/n ×180° )
 
 Each Sn is to be interpreted as a filled shape consisting of all points on the perimeter and in the interior.
 
@@ -23,37 +23,23 @@ The Minkowski sum, S+T, of two shapes S and T is the result of
 
 adding every point in S to every point in T, where point addition is performed coordinate-wise:
 
-(u, v) + (x, y) = (u+x, v+y).
+(u, v) + (x, y) = (u+x, v+y).
 
 For example, the sum of S3 and S4 is the six-sided shape shown in pink below:
 
+How many sides does S1864 + S1865 + … + S1909 have?
 
+# --hints--
 
+`euler228()` should return 86226.
 
-How many sides does S1864 + S1865 + … + S1909 have?
-</section>
-
-## Instructions
-<section id='instructions'>
-
-</section>
-
-## Tests
-<section id='tests'>
-
-```yml
-tests:
-  - text: <code>euler228()</code> should return 86226.
-    testString: assert.strictEqual(euler228(), 86226);
-
+```js
+assert.strictEqual(euler228(), 86226);
 ```
 
-</section>
+# --seed--
 
-## Challenge Seed
-<section id='challengeSeed'>
-
-<div id='js-seed'>
+## --seed-contents--
 
 ```js
 function euler228() {
@@ -64,17 +50,8 @@ function euler228() {
 euler228();
 ```
 
-</div>
-
-
-
-</section>
-
-## Solution
-<section id='solution'>
+# --solutions--
 
 ```js
 // solution required
 ```
-
-</section>