Fix docs

doc/AddonStorageBackend.md

@@ -14,6 +14,7 @@ The class must implement `Friendica\Model\Storage\IStorage` interface. All metho
 
 namespace Friendica\Model\Storage;
 
+```php
 interface IStorage
 {
 	public static function get($ref);
@@ -22,6 +23,7 @@ namespace Friendica\Model\Storage;
 	public static function getOptions();
 	public static function saveOptions($data);
 }
+```
 
 - `get($ref)` returns data pointed by `$ref`
 - `put($data, $ref)` saves data in `$data` to position `$ref`, or a new position if `$ref` is empty.
@@ -196,7 +198,7 @@ function samplestorage_unistall()
 	// when the plugin is uninstalled, we unregister the backend.
 	StorageManager::unregister("Sample Storage");
 }
-
+```