STL in C++ course(bangla) added (#10478)

* Competitive programming youtube channel in bengali

* competitive programming youtube channel in bengali

* competitive programming channel in bengali

* fixes issue #9959

* updated

* Update courses/free-courses-bn.md

Co-authored-by: Eric Hellman <eric@hellman.net>

* Competitive Programming beginner course added

* ordering updated

* ordering updated

* Competitive Programming course in english

* STL in C++ (bangla) course added

* Updated free-courses-bn.md

* Update free-courses-en.md

* Update free-courses-hi.md

* Update free-courses-bn.md

---------

Co-authored-by: Eric Hellman <eric@hellman.net>

courses/free-courses-bn.md

@@ -69,10 +69,9 @@
 ### <a id="cpp"></a>C++
 
 * [C++ Bangla Tutorial Course](https://www.youtube.com/playlist?list=PLgH5QX0i9K3q0ZKeXtF--CZ0PdH1sSbYL) - Anisul Islam
-* [C++ Bangla Tutorial for Beginners - 2022](https://www.youtube.com/playlist?list=PLeqnvPK4PpyWsjZvgLTRcc-dkPQXc8SHc) - 
-Shikkhangon BD
-* [Object Oriented C++ \| Bangla Tutorial](https://www.youtube.com/playlist?list=PLy7uM3PHzMF1hnqhFGE4_A8qTUfFmZ_3y) - 
-Online School
+* [C++ Bangla Tutorial for Beginners - 2022](https://www.youtube.com/playlist?list=PLeqnvPK4PpyWsjZvgLTRcc-dkPQXc8SHc) - Shikkhangon BD
+* [C++ STL (Bangla)](https://youtube.com/playlist?list=PLgLCjVh3O6Sgux985GYG22xkFt9z9Sq0_) - LoveExtendsCode
+* [Object Oriented C++ \| Bangla Tutorial](https://www.youtube.com/playlist?list=PLy7uM3PHzMF1hnqhFGE4_A8qTUfFmZ_3y) - Online School
 
 
 ### Competitive Programming