add select all role for macOS

fixes #19003

src/vs/platform/menubar/electron-main/menubar.ts

@@ -652,6 +652,8 @@ export class Menubar {
 				options['role'] = 'copy';
 			} else if (commandId === 'editor.action.clipboardPasteAction') {
 				options['role'] = 'paste';
+			} else if (commandId === 'editor.action.selectAll') {
+				options['role'] = 'selectAll';
 			}
 
 			// Add context aware click handlers for special case menu items