HackStudio: Embed a Terminal widget below the text editor

This will be very useful for running (and interacting with) programs
after we build them. :^)

DevTools/HackStudio/TerminalWrapper.h

@@ -0,0 +1,16 @@
+#pragma once
+
+#include <LibGUI/GWidget.h>
+
+class TerminalWidget;
+
+class TerminalWrapper final : public GWidget {
+    C_OBJECT(TerminalWrapper)
+public:
+    virtual ~TerminalWrapper() override;
+
+private:
+    explicit TerminalWrapper(GWidget* parent);
+
+    RefPtr<TerminalWidget> m_terminal_widget;
+};