[ADF-2463] Moved core components to subfolder (#3062)

docs/core/storage.service.md

@@ -0,0 +1,44 @@
+---
+Added: v2.0.0
+Status: Active
+---
+# Storage service
+
+Stores items in the form of key-value pairs.
+
+## Methods
+
+-   `getItem(key: string): string`  
+    Gets an item.  
+    -   `key` - Key to identify the item
+-   `setItem(key: string, data: string)`  
+    Stores an item  
+    -   `key` - Key to identify the item
+    -   `data` - Data to store
+-   `clear()`  
+    Removes all currently stored items.   
+
+-   `removeItem(key: string)`  
+    Removes a single item.  
+    -   `key` - Key to identify the item
+-   `hasItem(key: string): boolean`  
+    Is any item currently stored under `key`?  
+    -   `key` - Key identifying item to check
+
+## Details
+
+The service will check to see if
+[web storage](https://developer.mozilla.org/en-US/docs/Web/API/Storage/LocalStorage)
+is available on the browser. If it is available then the service will use it to
+store the key-value items persistently. Web storage can be used in a similar way to
+[cookies](cookie.service.md) but with a much higher size limit (several MB for
+web storage compared to a few KB for cookies). However, cookies are
+more widely supported by browsers and can be set to expire after a certain date.
+
+If local storage is not available then non-persistent memory storage within the app is
+used instead.
+
+## See also
+
+-   [Cookie service](cookie.service.md)
+-   [Content service](content.service.md)