docs(readme): mention URL shortening

README.md

@@ -14,7 +14,7 @@ some text
 
 ## Features
 
-- File upload
+- File upload & URL shortening
   - supports basic HTTP authentication
   - random file names (optional)
     - pet name (e.g. `capital-mosquito.txt`)
@@ -51,6 +51,12 @@ $ rpaste x.txt
 $ rpaste -
 ```
 
+#### URL Shortening
+
+```sh
+curl -F "url=https://example.com/some/long/url" "<server_address>"
+```
+
 ### Server
 
 To start the server: