fix: replace .english.md extension with .md

curriculum/challenges/english/10-coding-interview-prep/project-euler/problem-166-criss-cross.md

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+---
+id: 5900f4131000cf542c50ff25
+challengeType: 5
+title: 'Problem 166: Criss Cross'
+forumTopicId: 301800
+---
+
+## Description
+<section id='description'>
+A 4x4 grid is filled with digits d, 0 ≤ d ≤ 9.
+
+It can be seen that in the grid
+
+
+6 3 3 0
+5 0 4 3
+0 7 1 4
+1 2 4 5
+
+the sum of each row and each column has the value 12. Moreover the sum of each diagonal is also 12.
+
+In how many ways can you fill a 4x4 grid with the digits d, 0 ≤ d ≤ 9 so that each row, each column, and both diagonals have the same sum?
+</section>
+
+## Instructions
+<section id='instructions'>
+
+</section>
+
+## Tests
+<section id='tests'>
+
+```yml
+tests:
+  - text: <code>euler166()</code> should return 7130034.
+    testString: assert.strictEqual(euler166(), 7130034);
+
+```
+
+</section>
+
+## Challenge Seed
+<section id='challengeSeed'>
+
+<div id='js-seed'>
+
+```js
+function euler166() {
+
+  return true;
+}
+
+euler166();
+```
+
+</div>
+
+
+
+</section>
+
+## Solution
+<section id='solution'>
+
+```js
+// solution required
+```
+
+</section>