Unity / Quest - read a JSON config file stored locally on device

Hi all

I'm currently developing a virtual art studio for the Quest.  My app currently loads png's from an external web url.  This url is specified as a variable in Unity and thus gets "baked in" at compilation time.  What I'd like to have is a JSON file locally on the device that the user can edit and specify the url (so they can load their own images).  Can this be done and if so, does anyone have some sample code or resources I could look at?

Many thanks in advance.