How to customize the file name

## 💬 Questions and Help

I tried using
`
var file = await DefaultCacheManager().getSingleFile('https:xxx.com/test.pdf')
`
but I got a file with a path
`
'/cache/libCachedImageData/1f91faa0-a9dd-1df7-98e4-0df546dcdedb.pdf"
`

Start with the DefaultCacheManager().getSingleFile('https:xxx.com/test.pdf') usage shown in the issue and inspect the cache manager API documentation and entry point for file naming. Done means documenting whether callers can customize the cached file name and, if supported, explaining the relevant option.

Scritto dal modello di indicizzazione a partire dal testo della issue.