Documentation (mostly for scenes) (#58)

Former-commit-id: 76fe4a261710ff744d09c9dd0a9b694f759fda41

examples/doc_unVar.hs

@@ -0,0 +1,13 @@
+#!/usr/bin/env stack
+-- stack runghc --package reanimate
+module Main(main) where
+
+import Reanimate
+import Reanimate.Builtin.Documentation
+
+main :: IO ()
+main = reanimate $ docEnv $ sceneAnimation $ do
+  v <- newVar 0
+  _ <- newSprite $ mkCircle <$> unVar v
+  tweenVar v 1 $ \val -> fromToS val 3
+  tweenVar v 1 $ \val -> fromToS val 0