New plugin hook: ability to add custom filters to Shaarli search engine

A new plugin hook has been added: hook_test_filter_search_entry
This hook allows to filter out bookmark with custom plugin code when a search is performed.

Related to #143

tests/plugins/test/test.php

@@ -1,5 +1,7 @@
 <?php
 
+use Shaarli\Bookmark\Bookmark;
+
 /**
  * Hook for test.
  *
@@ -43,3 +45,8 @@ function test_register_routes(): array
         ],
     ];
 }
+
+function hook_test_filter_search_entry(Bookmark $bookmark, array $context): bool
+{
+    return $context['_result'];
+}