Add www/screego

Screego allows to share a screen with good quality and low latency.
It is just an addition to existing software and only helps to share a screen,
nothing else.

Features:

• Multi user screenshare
• Secure transfer via WebRTC
• Low latency / High resolution
• Integrated TURN server (see NAT Traversal documentation)

WWW: https://github.com/screego/server

Differential Revision: https://reviews.freebsd.org/D27090