LibGUI: Create thumnail for gif files

Author: https://github.com/asliturk
Commit: c9c1d1fae0
Pull-request: https://github.com/SerenityOS/serenity/pull/1956
Reviewed-by: https://github.com/awesomekling
Reviewed-by: https://github.com/linusg

Libraries/LibGUI/FileSystemModel.cpp

@@ -440,7 +440,7 @@ Icon FileSystemModel::icon_for_file(const mode_t mode, const String& name) const
 
 Icon FileSystemModel::icon_for(const Node& node) const
 {
-    if (node.name.to_lowercase().ends_with(".png")) {
+    if (node.name.to_lowercase().ends_with(".png") || node.name.to_lowercase().ends_with(".gif")) {
         if (!node.thumbnail) {
             if (!const_cast<FileSystemModel*>(this)->fetch_thumbnail_for(node))
                 return m_filetype_image_icon;