Add hash of file in metadata for airdrops

[yabirgb]

Currently we can't enforce updates to airdrops files and if we need to change something we have to request users to delete the .csv files.

To improve this we need:

• In the data repo provide a hash field with the hash of the csv file
• the app should check with the cached information if the hashes match. If they don't the local csv file should be deleted and queried again