How to update a JSON file automatically in a GitHub repo when another file is update manually

Question

I am Peter and I am a Siri Shortcuts creator. What my problem is that I store my images (base64) in a json file. In my ‘shortcut’ I use a cache system so it won’t download every-time. What I want to do is every time a new version came out of that json file, I want to update another file with a version number (commit 1 is v1-V2, commit 2 is v2-v3 and so one). I want that version number to update automatically every time I update the base64 json file. I want that to happen so I can check in my shortcut every time if a cache update is needed.

I don’t know how to this so help would be appreciated!