Mention default state in safety manual FAQ

It might be a good idea to explain that the default state for the QML type is implicit, and it consumes one state from the maximum number of states 

(see https://doc-snapshots.qt.io/qtsaferenderer/saferenderer-constraints.html#MAX_NUM_OF_STATES-var)

By default the value is eight, therefore user can add seven states, not eight states, because the default state needs to be counted. But it is not visible since it is implicitly defined.

This default state is not included in the linked Qt documentation, and the limitation is QSR specific thing due to static memory allocation.

And the name of the default state is "" (empty string) when referring to it in transitions in the QML. Or when sending an createStateChangeEvent. 

This topic is popping up, so it is frequently asked question