update URL docs in README.md
@@ -122,8 +122,12 @@ The request body can also be read from standard input, or from a file using `@fi
### Shorthand form for URLs
-Similar to HTTPie, specifying the scheme portion of the request URL is optional. `xh` also supports
-omitting `localhost` from the URL as long it starts with colon plus an optional port number.
+Similar to HTTPie, specifying the scheme portion of the request URL is optional. A leading colon works as shorthand
+for localhost. `:8000` is equivalent to `localhost:8000`, and `:/path` is equivalent to `localhost/path`.
+
+URLs can have a leading `://` which allows quickly converting a URL into a valid xh or HTTPie command. For example
+`http://httpbin.org/json` becomes `http ://httpbin.org/json`.
+
```sh
xh http://localhost:3000/users # resolves to http://localhost:3000/users
