Update edge_system.md

[AmirhosseinR]

Add NLU Paper

• NLU: An Adaptive, Small-Footprint, Low-Power Neural Learning Unit for Edge and IoT Applications [Paper]
  • A. Rostami et al., IEEE Open Journal of Circuits and Systems, vol. 6, pp. 85-99, 2025
  • IEEE Open Journal of Circuits and Systems
  • Summary: This paper presents the Neural Learning Unit (NLU), a tiny, low-power, and flexible hardware accelerator designed to enable real-time training of neural networks directly on edge