[packages/doc] define and document package rules

Central place for putting package-related info. This document or parts
of it can also be easily ported to other places if deemed appropriate.

doc/README.md

@@ -82,6 +82,7 @@ The Bitcoin repo's [root README](/README.md) contains relevant information on th
 - [Reduce Memory](reduce-memory.md)
 - [Reduce Traffic](reduce-traffic.md)
 - [Tor Support](tor.md)
+- [Transaction Relay Policy](policy/README.md)
 - [ZMQ](zmq.md)
 
 License