Tutorial for creating new sensors

The QTBUG-110939 removes the Grue example application whose main purpose is to demonstrate how to create one's own sensors.

However, while a nice implementation, it doesn't fill that purpose particularly well.
And in addition the example does not build/deploy well on all platforms, all in all being a slightly too complex construct considering its straightforward primary purpose.

This task is about creating a tutorial-like step-by-step documentation for creating one's own sensors.