Notify users of the availability of the MCU QDS documentation guide when creating a MCU project

Qt MCUs docs not easy to locate in the Getting Started content Content.

To make it easy to find, especially for newcomers of either QDS or MCU, we could add a notification that links to the correct MCU page (https://doc.qt.io/qtdesignstudio/studio-on-mcus.html) right after creating a new MCU project. The users should have an option such as "Don't show again" to not show this notification if he/she doesn't need it.