Adding Haskell examples (#17)

* Adding binary search example for Haskell

* Adding selection sort example in Haskell

* Adding Haskell examples for chapter 3

* Adding examples for chapter 4

* Adding examples for chapter 5

* Adding git ignore

* Add Haskell example for BFS

03_recursion/Haskell/01_countdown.hs

@@ -0,0 +1,9 @@
+countdown :: Integer -> IO()
+countdown n
+  | n < 0 = return ()
+  | otherwise = do
+      putStrLn (show n)
+      countdown (n-1)
+
+main = do
+  countdown 5