* fix: corrected method return value following Dart's newest linter version
* feat: added Dart recursion examples for chapter 3
* feat: added quicksort example in Dart for chapter 4
* feat: added examples in Dart for the chapter 5
* feat: added Dart example for chapter 6 bfs
* feat: added djikstra example in Dart for chapter 7
* feat: added example of set covering in Dart for chapter 8
* feat: added examples for dynamic programming in dart for chapter 9
