Fixed issue #7015: Access Multi-Dimensional Arrays with Indexes

This commit clarifies the explanation and example for the Basic Javascript challenge "Access Multi-Dimensional Arrays with Indexes." The implemented fix was proposed by @erictleung in https://github.com/FreeCodeCamp/FreeCodeCamp/issues/7015#issuecomment-222345491

challenges/01-front-end-development-certification/basic-javascript.json

@@ -1756,9 +1756,9 @@
       "id": "56592a60ddddeae28f7aa8e1",
       "title": "Access Multi-Dimensional Arrays With Indexes",
       "description": [
-        "One way to think of a <dfn>multi-dimensional</dfn> array, is as an <em>array of arrays</em>. When you use brackets to access your array, the first set of bracket refers to the entries in the outer-most array, and each subsequent level of brackets refers to the next level of entries inside.",
+        "One way to think of a <dfn>multi-dimensional</dfn> array, is as an <em>array of arrays</em>. When you use brackets to access your array, the first set of bracket refers to the entries in the outer-most (the first level) array, and each additional pair of brackets refers to the next level of entries inside.",
         "<strong>Example</strong>",
-        "<blockquote>var arr = [<br>    [1,2,3],<br>    [4,5,6],<br>    [7,8,9],<br>    [[10,11,12], 13, 14]<br>];<br>arr[0]; // equals [1,2,3]<br>arr[1][2]; // equals 6<br>arr[3][0][1]; // equals 11</blockquote>",
+        "<blockquote>var arr = [<br>    [1,2,3],<br>    [4,5,6],<br>    [7,8,9],<br>    [[10,11,12], 13, 14]<br>];<br>arr[3]; // equals [[10,11,12], 13, 14]<br>arr[3][0]; // equals [10,11,12]<br>arr[3][0][1]; // equals 11</blockquote>",
         "<h4>Instructions</h4>",
         "Using bracket notation select an element from <code>myArray</code> such that <code>myData</code> is equal to <code>8</code>."
       ],