chore: init bangla book-courses split

Via https://github.com/EbookFoundation/free-programming-books/issues/6591

README.md

@@ -79,6 +79,7 @@ Please read [CONTRIBUTING](CONTRIBUTING.md). If you're new to GitHub, [welcome](
 ### Free Online Courses
 
 + [Arabic / al arabiya / العربية](courses/free-courses-ar.md)
++ [Bengali / বাংলা](courses/free-courses-bn.md)
 + [Bulgarian / български](courses/free-courses-bg.md)
 + [English](courses/free-courses-en.md)
 + [Finnish](courses/free-courses-fi.md)

books/free-programming-books-bn.md

@@ -1,4 +1,3 @@
-
 ### Index
 
 * [Android](#android)

courses/free-courses-bn.md

@@ -0,0 +1,3 @@
+### Index
+
+<!-- Waiting to add in -->