add geode::Dropdown and replace one-of arrows with dropdown

loader/include/Geode/ui/Dropdown.hpp

@@ -0,0 +1,45 @@
+#pragma once
+
+#include <Geode/DefaultInclude.hpp>
+#include <Geode/utils/function.hpp>
+#include <cocos2d.h>
+#include <string>
+#include <vector>
+
+class DropdownOverlay;
+
+namespace geode {
+    class GEODE_DLL Dropdown : public cocos2d::CCNode {
+        class Impl;
+        std::unique_ptr<Impl> m_impl;
+
+        friend class ::DropdownOverlay;
+
+    protected:
+        Dropdown();
+        ~Dropdown() override;
+
+        bool init(
+            float width, std::vector<std::string> options,
+            Function<void(std::string const&, size_t)> callback
+        );
+
+        void onOpen(cocos2d::CCObject*);
+
+    public:
+        static Dropdown* create(
+            float width, std::vector<std::string> options,
+            Function<void(std::string const&, size_t)> callback
+        );
+
+        void setSelected(size_t index);
+        void setSelected(std::string_view value);
+        size_t getSelectedIndex() const;
+        std::string getSelectedValue() const;
+
+        void setEnabled(bool enabled);
+        bool isEnabled() const;
+
+        void setItems(std::vector<std::string> options);
+    };
+}