Add demo_slowuav.py
Add demo_slowuav.py

It shows a quite slow UAV doing some planned trajectory, depicting the
non-stationarity property of the observation task

fire-rs-laas/fire-rs-saop,fire-rs-laas/fire-rs-saop,fire-rs-laas/fire-rs-saop,fire-rs-laas/fire-rs-saop