Control buttons can be added to the window's header with `lv_win_add_btn_right(win, icon, btn_width)`. `icon` can be any image source, and `btn_width` is the width of the button.
The title and the buttons will be added in the order of the functions are called. So adding a button, a text and two other buttons will result in a button on the left, a title, ant 2 buttons on the right.
The width of the title is set to take all the remaining space on the header. In other words it pushes the buttons to the right added after the title.
`lv_win_get_header(win)` return a pointer to the header, `lv_win_get_content(win)` returns a pointer to the content container to which the content of the window can be added.