feat: Add unduck search engine

Author: Pinguin2001

src/Core/SearchEngineHelper.cs

@@ -32,6 +32,7 @@ public static void SetSearchEngine(SearchEngine engine, SearchEngineType engineT
         new("Google", "https://www.google.com/search?q="),
         new("Startpage", "https://www.startpage.com/search?q="),
         new("Qwant", "https://www.qwant.com/?q="),
+        new("Unduck", "https://unduck.link?q="),
         new("Yahoo!", "https://search.yahoo.com/search?p="),
         new("Yandex", "https://yandex.com/search/?text=")
     };