README.md: Explain that companion nodes do not repeat messages

This is a key difference compared to other systems and I see people
asking this a lot. It is mentioned in the FAQ but let's make it more
prominent in the README.

README.md

@@ -9,7 +9,10 @@ MeshCore provides the ability to create wireless mesh networks, similar to Mesht
 
 ## ⚡ Key Features
 
-* Multi-Hop Packet Routing – Devices can forward messages across multiple nodes, extending range beyond a single radio's reach. MeshCore supports up to a configurable number of hops to balance network efficiency and prevent excessive traffic.
+* Multi-Hop Packet Routing
+  * Devices can forward messages across multiple nodes, extending range beyond a single radio's reach.
+  * Supports up to a configurable number of hops to balance network efficiency and prevent excessive traffic.
+  * Nodes use fixed roles where "Companion" nodes are not repeating messages at all to prevent adverse routing paths from being used.
 * Supports LoRa Radios – Works with Heltec, RAK Wireless, and other LoRa-based hardware.
 * Decentralized & Resilient – No central server or internet required; the network is self-healing.
 * Low Power Consumption – Ideal for battery-powered or solar-powered devices.