Move windows to uptr. Add simple text editing.

src/ui_elements/widgets/TextBox.h

@@ -0,0 +1,29 @@
+#pragma once
+
+#include "Widget.h"
+
+class TextBox : public Widget
+{
+private:
+
+    std::string mContent;
+    bool mCaps;
+
+public:
+
+    TextBox();
+
+    static std::unique_ptr<TextBox> Create();
+
+    void SetContent(const std::string& text);
+
+    std::string GetContent() const;
+
+    void AppendContent(const std::string& text);
+
+    void OnPaintEvent(const PaintEvent* event) override;
+
+    bool OnMyKeyboardEvent(const KeyboardEvent* event) override;
+};
+
+using TextBoxUPtr = std::unique_ptr<TextBox>;