Add docs to storage module (#7)

Author: elliotdavies

src/Web/Storage/Storage.purs

@@ -1,3 +1,5 @@
+-- | This module defines a data type and various functions for interacting
+-- | with the `Storage` interface of the Web Storage API.
 module Web.Storage.Storage
   ( Storage
   , length
@@ -16,20 +18,26 @@ import Effect (Effect)
 
 foreign import data Storage :: Type
 
+-- | Returns the number of items in the storage.
 foreign import length :: Storage -> Effect Int
 
 foreign import _key :: Int -> Storage -> Effect (Nullable String)
 
+-- | Retrieves the key at the given index in the storage, if one exists.
 key :: Int -> Storage -> Effect (Maybe String)
 key i = map toMaybe <<< _key i
 
 foreign import _getItem :: String -> Storage -> Effect (Nullable String)
 
+-- | Retrieves the value stored at the given key, if one exists.
 getItem :: String -> Storage -> Effect (Maybe String)
 getItem s = map toMaybe <<< _getItem s
 
+-- | Given a key name and a value (in that order), adds that key to the storage or updates its value if it already exists.
 foreign import setItem :: String -> String -> Storage -> Effect Unit
 
+-- | Removes the given key from the storage.
 foreign import removeItem :: String -> Storage -> Effect Unit
 
+-- | Clears all keys from the storage.
 foreign import clear :: Storage -> Effect Unit