Add BFS and DFS for tree.

Author: trekhleb

README.md

@@ -111,7 +111,7 @@ npm test -- -t 'playground'
 
 ## Useful links
 
-* [📹 Data Structures and Algorithms on YouTube](https://www.youtube.com/playlist?list=PLLXdhg_r2hKA7DPDsunoDZ-Z769jWn4R8)
+* [Data Structures and Algorithms on YouTube 📹](https://www.youtube.com/playlist?list=PLLXdhg_r2hKA7DPDsunoDZ-Z769jWn4R8)
 
 ## Useful Information