Add sha3/bmt hash field to file metadata

[Igor Shadurin]

Currently, our metadata does not include a field for the hash of the entire file. This makes it difficult to verify the integrity of downloaded data.

I propose adding a sha3/bmt hash field to the metadata to allow for easy verification of the downloaded data. This will ensure that users can trust the data they are downloading and prevent any potential issues with corrupted files.

wdyt @nugaon?