make package comments more descriptive

A lot has happened since the 'package rsync' one was written :)

Package rsyncd is the package that gets imported the most currently,
so ensure it also has a complete description.

doc.go

@@ -1,4 +1,7 @@
-// Package rsync contains a native Go rsync implementation.
+// Package rsync (gokrazy/rsync) contains a native Go rsync implementation that
+// supports sending and receiving files as client or server, compatible with the
+// original tridge rsync (from the samba project) or openrsync (used on OpenBSD
+// and macOS 15+).
 //
 // The only component currently is gokr-rsyncd, a read-only rsync daemon
 // sender-only Go implementation of rsyncd. rsync daemon is a custom

rsyncd/rsyncd.go

@@ -1,3 +1,7 @@
+// Package rsyncd implements an rsync server (only), but note that gokrazy/rsync
+// contains a native Go rsync implementation that supports sending and receiving
+// files as client or server, compatible with the original tridge rsync (from
+// the samba project) or openrsync (used on OpenBSD and macOS 15+).
 package rsyncd
 
 import (