readme: add basic example config

README.md

@@ -2,6 +2,15 @@
 
 A TLS reverse proxy.
 
+- Automatic TLS with Let's Encrypt
+- Route incoming connections to backends using Server Name Indication
+
+Example configuration:
+
+    frontend example.org:443 {
+        backend localhost:8080
+    }
+
 ## License
 
 MIT