Add wait_for_exit() method

Author: gammasoft71

examples/xtd.drawing.examples/graphics/graphics/src/graphics.cpp

@@ -17,5 +17,5 @@ auto main() -> int {
   graphics.fill_rectangle(brushes::white(), drawing_bitmap.width() / 2 + 50, drawing_bitmap.height() - 140, 70, 60);
   graphics.fill_polygon(linear_gradient_brush {rectangle {drawing_bitmap.width() / 2 - 160, drawing_bitmap.height() - 300, 320, 120}, color::brown, color::sandy_brown, linear_gradient_mode::backward_diagonal}, array<point> {{drawing_bitmap.width() / 2, drawing_bitmap.height() - 300}, {drawing_bitmap.width() / 2 + 160, drawing_bitmap.height() - 180}, {drawing_bitmap.width() / 2 - 160, drawing_bitmap.height() - 180}});
   drawing_bitmap.save(path::combine(path::get_temp_path(), "graphics.png"));
-  diagnostics::process::start(diagnostics::process_start_info {path::combine(path::get_temp_path(), "graphics.png")}.use_shell_execute(true));
+  diagnostics::process::start(diagnostics::process_start_info {path::combine(path::get_temp_path(), "graphics.png")}.use_shell_execute(true)).wait_for_exit();
 }