After many tries, one solution is 
:
1- In the dataloader : aggregate the data into a file at the root level : ./history.json (don’t try to put it into src or _file)
2- In Github Actions : cache the exact same file : history.json
But the history.json file at the root level cannot be downloaded any longer as a in a .md for instance.
Never mind there is a dynamic content solution How to download a file from framework ?