fix document naming and file dialogs preset, add touch scroll, flip thumbnail, scroll gesture and wheel for sidebar

engine/app.h

@@ -47,6 +47,7 @@ public:
     std::function<void(glm::vec4 color)> on_color_change;
     std::function<void()> on_stroke_change;
     const uint16_t main_id = const_hash("main");
+    std::string doc_name;
     float width;
     float height;
     bool keys[256];