[RSC] Implement Length Measure Utils

Implement a util function(s) to measure distance in real world

• Checkout realsense official sample (measure)
• Or directly use FOV
• Or use point cloud (checkout realsense-ros document) [Recommended]

For example:

• I want obstacle on route from 1m to 5m.
• Then we get image of all point from 1m to 5m.
• And cut the points of all point on the route, which will shape like a tunnel.