feat(Carpenter): add defaultUpdate

`defaultUpdate` is a default implementation of the update function which ignores all actions

docs/Carpenter.md

@@ -91,6 +91,15 @@ spec' :: forall state props action eff. state -> action -> Update state props ac
 Constructs a React component spec based on an initial state,
 an initial action, an update function and a render function.
 
+#### `defaultUpdate`
+
+``` purescript
+defaultUpdate :: forall state props action eff. Update state props action eff
+```
+
+A default implementation for the update function which does not perform
+any changes to the state, that is, ignores all actions.
+
 #### `mockUpdate`
 
 ``` purescript

src/Carpenter.purs

@@ -8,6 +8,7 @@ module Carpenter
   , EventHandler
   , ActionHandler
   , CarpenterEffects
+  , defaultUpdate
   , mockUpdate
   ) where
 
@@ -87,6 +88,11 @@ spec' state action update render = (React.spec state (getReactRender update rend
       let dispatch = mkDispatcher this update yield
       unsafeInterleaveEff (launchAff (update yield dispatch action props state))
 
+-- | A default implementation for the update function which does not perform
+-- | any changes to the state, that is, ignores all actions.
+defaultUpdate :: ∀ state props action eff. Update state props action eff
+defaultUpdate _ _ _ _ = pure
+
 -- | Generates an update function for testing with mock `yield` and `dispatch`
 -- | functions, which do not depend on React, but return the modified state and
 -- | behave as expected.