Support generic way to get informations/status of a key

[farnabaz]

It would be great if unstorage drivers provide informations/stats about the keys. This information could be helpful.

For example one of the important informations about the keys is the last modified date. Last modified date is used in Nuxt Content and Docus to show updated date of document.

[pi0]

Hi. You can store it in a sibling key like /content/foo => /content/foo.meta. I plan to support built-in meta handling but it cannot always support features like mtime due to driver limitations.