How to set Focus to Mainwindow

Fixed two things in the example:

Fixed the active_window() method name, was supposed to be named activate_window().

In the second method, the application module is named Sketchup, not SketchUp, so fixed the call to the is_pro? module function.

Which is exactly why we have begging for for years for an API module function to set the SketchUp application window to have the focus, regardless of platform, language build, or SketchUp edition (Pro / Make.)