Expand README, slightly

Author: ammario

README.md

@@ -1,3 +1,13 @@
-# wush - wireguard powered shells and file transfers behind nat
+# wush
 
 [![Go Reference](https://pkg.go.dev/badge/github.com/coder/wush.svg)](https://pkg.go.dev/github.com/coder/wush)
+
+`wush` is a command line tool that lets you easily transfer
+files and open shells over a peer-to-peer wireguard connection. It's similar to [magic-wormhole](https://github.com/magic-wormhole/magic-wormhole) but doesn't require you to
+set up a relay server.
+
+## Basic Usage
+
+```
+go install github.com/coder/wush/cmd/wush@latest
+```