feat: QComboBox and QPlainTextEdit

QComboBox（下拉列表框）和QPlainTextEdit（可同时编辑多行的富文本编辑器）的介绍和使用

QtQcomboBoxEx/ExQcomboBox.h

@@ -0,0 +1,32 @@
+#ifndef EXQCOMBOBOX_H
+#define EXQCOMBOBOX_H
+
+#include <QWidget>
+
+namespace Ui {
+class ExQcomboBox;
+}
+
+class ExQcomboBox : public QWidget
+{
+    Q_OBJECT
+
+public:
+    explicit ExQcomboBox(QWidget *parent = nullptr);
+    ~ExQcomboBox();
+
+private slots:
+    void on_btnLeftInit_clicked();
+    void on_btnLeftClear_clicked();
+    void on_checkBoxOnlyWrite_clicked();
+    void on_btnRightInit_clicked();
+    void on_btnBottomAdd_clicked();
+    void on_btnBottomClear_clicked();
+    void on_checkBoxOnlyRead_clicked();
+    void onSelectDisplay(QString str);
+
+private:
+    Ui::ExQcomboBox *ui;
+};
+
+#endif // EXQCOMBOBOX_H