循环滚动修复几处小逻辑问题；更新 README (滚动转换改为循环转换，字符串转换改为变量转换)

src/extension-handler/status-bar-handler.ts

@@ -11,7 +11,7 @@ let statusBar: vscode.StatusBarItem;
  */
 export function createStatusBarItem() {
     statusBar = vscode.window.createStatusBarItem(vscode.StatusBarAlignment.Left);
-    statusBar.text = '$(find-replace)字符串转换';
+    statusBar.text = '$(find-replace)变量转换';
     statusBar.command = 'variable-conversion.convertCase';
     // statusBar.color = 'red';
     // statusBar.show();