[server] Add very simple animation module

I mostly used this module for testing the partial tree updates.

src/Forest/TreeModule/AnimateModule.hs

@@ -0,0 +1,26 @@
+{-# LANGUAGE OverloadedStrings #-}
+
+module Forest.TreeModule.AnimateModule
+  ( AnimateModule
+  , animateModule
+  ) where
+
+import Control.Concurrent
+
+import           Forest.TreeModule
+import           Forest.Node
+import           Forest.Util
+
+data AnimateModule = AnimateModule
+
+instance TreeModule AnimateModule where
+
+animateModule :: Int -> [Node] -> ModuleConstructor AnimateModule
+animateModule delay frames sendNode continue =
+  withThread (animateThread frames) $ continue AnimateModule
+  where
+    animateThread [] = sendNode $ txtNode "" "Invalid animation: No frames provided"
+    animateThread (x:xs) = do
+      sendNode x
+      threadDelay delay
+      animateThread $ xs ++ [x]