Add haskell solution to Compute the Area of a Polygon

1 - Introduction/25 - Compute the Area of a Polygon/viniciusfk9.hs

@@ -0,0 +1,11 @@
+import Control.Monad
+
+f (p1, p2) (q1, q2) = fromIntegral (p1 * q2 - q1 * p2)
+
+area lst = 0.5 * fromIntegral (abs . sum $ zipWith f lst (tail lst))
+
+main = do
+    n <- fmap (read::String->Int) getLine
+    func <- forM [1..n] (\_->do
+      fmap ((\[a, b]->(a,b)) . map (read::String->Int).words) getLine :: IO (Int, Int))
+    putStrLn $ show (area (func ++ take 1 func))