Add Resource (competitive programming) in free-courses-bn.md (#7254)

* Update free-courses-bn.md

* Update free-courses-bn.md

Author: RaiyanMahin

courses/free-courses-bn.md

@@ -4,6 +4,7 @@
 * [C](#c)
 * [C#](#csharp)
 * [C++](#cpp)
+* [Competitive Programming](#competitive-programming)
 * [Dart](#dart)
 * [Flutter](#flutter)
 * [Git](#git)
@@ -55,6 +56,11 @@
 * [C++ Bangla Tutorial Course](https://www.youtube.com/playlist?list=PLgH5QX0i9K3q0ZKeXtF--CZ0PdH1sSbYL) - Anisul Islam
 
 
+### Competitive Programming
+
+* [Competitive Programming Course in Bengali](https://www.youtube.com/channel/UCozCCU3b1HmcmCf2gLN_7HA/videos) - Bangladesh IOI team
+
+
 ### Dart
 
 * [Dart All You Need To Know](https://www.youtube.com/playlist?list=PL_XxuZqN0xVC2-nXUrvpcQEz3FgCSIQHT) - Stack Learner