Added bengali textbook for C++ progamming (#7522)

* Update free-programming-books-bn.md

* Update free-programming-books-bn.md

* Update free-programming-books-bn.md

* fix: use an alias anchor for C++ deambiguation

Co-authored-by: David Ordás <3125580+davorpa@users.noreply.github.com>

books/free-programming-books-bn.md

@@ -3,6 +3,7 @@
 * [Algorithms](#algorithms)
 * [Data Science](#data-science)
 * [C](#c)
+* [C++](#cpp)
 * [Go](#go)
 * [Java](#java)
 * [JavaScript](#javascript)
@@ -21,6 +22,11 @@
 * [Computer Programming «কম্পিউটার প্রোগ্রামিং ১ম খণ্ড»](https://cpbook.subeen.com) - Tamim Shahriar Subeen (HTML)
 
 
+### <a id="cpp"></a>C++
+
+* [সিপিপি পরিগণনা Computer Programming](https://www.academia.edu/16658418/c_programming_bangla_book) - Mahmudul Hasan (PDF, HTML)
+
+
 ### Data Science
 
 * [ডাটা সাইন্সের হাতেখড়ি](https://datasinsightsbd.gitbook.io) - Fazle Rabbi Khan (gitbook)