The way you have written this will not work as a URL is not a path on the file system.
The closest way to implement what you want is to use an http service that have some storage, and use
HTTPClient to communicate with it.
It is quite simple, and many cloud providers have a free tier that may be sufficient for your needs.
You write your own service or use an a "key-value" database. If you are afraid touching these subjects yourself, you can try a complete "key value" cloud service such as this one.
For example, you could request
get the list of high scores and
put a new high score in the list.
Notice though, that this makes your game hackable, as anybody could send these requests and set any high score for any player.