TextEditor: Added a setter for soft_tab_width

Userland/Libraries/LibGUI/TextEditor.h

@@ -85,6 +85,7 @@ public:
     void set_automatic_indentation_enabled(bool enabled) { m_automatic_indentation_enabled = enabled; }
 
     virtual int soft_tab_width() const final { return m_soft_tab_width; }
+    void set_soft_tab_width(int width) { m_soft_tab_width = width; };
 
     WrappingMode wrapping_mode() const { return m_wrapping_mode; }
     bool is_wrapping_enabled() const { return m_wrapping_mode != WrappingMode::NoWrap; }