Add tasks for all the new languages

Task/Fast-Fourier-transform/Idris/fast-fourier-transform.idris

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+module Main
+
+import Data.Complex
+
+
+concatPair : List (a, a) -> List (a)
+concatPair xs with (unzip xs)
+  | (xs1, xs2) = xs1 ++ xs2
+
+fft' : List (Complex Double) -> Nat -> Nat -> List (Complex Double)
+fft' (x::xs) (S Z) _ = [x]
+fft' xs n s = concatPair $ map (\(x1,x2,k) =>
+                let eTerm = ((cis (-2 * pi * ((cast k) - 1) / (cast n))) * x2) in
+                  (x1 + eTerm, x1 - eTerm)) $ zip3 left right [1..n `div` 2]
+
+             where
+                  left : List (Complex Double)
+                  right : List (Complex Double)
+                  left  = fft' (xs) (n `div` 2) (2 * s)
+                  right = fft' (drop s xs) (n `div` 2) (2 * s)
+
+
+-- Recursive Cooley-Tukey with radix-2 DIT case
+-- assumes no of points provided are a power of 2
+fft : List (Complex Double) -> List (Complex Double)
+fft [] = []
+fft xs = fft' xs (length xs) 1
+
+
+main : IO()
+main = traverse_ printLn $ fft [1,1,1,1,0,0,0,0]