sync with 2.3.9

guide/project_examples.md

@@ -177,10 +177,12 @@ v2.2.9 or higher:
 
 ```lua
 target("qt_widgetapp")
-    add_rules("qt.widgetapp")
-    add_files("src/*.cpp")
+    add_rules("qt.widgetapp")
+    add_headerfiles("src/*.h")
+    add_files("src/*.cpp")
     add_files("src/mainwindow.ui")
-    add_files("src/mainwindow.h")  -- add files with Q_OBJECT meta (only for qt.moc)
+    -- add files with Q_OBJECT meta (only for qt.moc)
+    add_files("src/mainwindow.h")
 ```
 
 !> The new version provides the `qt.widgetapp` rule, built-in QtWidgets built-in rules, the use of simpler, the following version of the `qt.application` is still supported, backward compatible: