Added a course resource. (Changes Made) (#9658)

* added resources in courses

* Update free-courses-en.md

* Added escape I

courses/free-courses-en.md

@@ -183,6 +183,7 @@
 * [Sorting Algorithms](https://www.youtube.com/playlist?list=PL2_aWCzGMAwKedT2KfDMB9YA5DgASZb3U) - mycodeschool
 * [Stanford University Algorithms: Design and Analysis, Part 1](https://online.stanford.edu/courses/soe-ycsalgorithms1-algorithms-design-and-analysis-part-1)
 * [Stanford University Algorithms: Design and Analysis, Part 2](https://online.stanford.edu/courses/soe-ycs0001-algorithms-design-and-analysis-part-2)
+* [Strivers A2Z-DSA Course \| DSA Playlist \| Placements](https://www.youtube.com/playlist?list=PLgUwDviBIf0oF6QL8m22w1hIDC1vJ_BHz) - take U forward
 * [Trees by Striver \| C++ \| Java \| Placements \| Binary Trees and Traversals \| Problems](https://www.youtube.com/playlist?list=PLgUwDviBIf0q8Hkd7bK2Bpryj2xVJk8Vk) - take U forward