docs: add url usage example

README.md

@@ -13,7 +13,11 @@ Meant to be used with Docker, but it would work locally if you have [youtube-dl]
 docker run -it --rm -p 8080:8080 -v $PWD/data:/app/data w33ble/youtube-dl-web
 ```
 
-Then hit `http://localhost:8080`, passing in a `url` and optionally a `format` query parameter for where to download from.
+Then hit `http://localhost:8080`, passing in a `url` and optionally a `format` query parameter for where to download from. For example:
+
+```text
+http://localhost:8080?url=https://www.youtube.com/watch?v=YE7VzlLtp-4
+```
 
 ### Automatic cleanup