EXIF has a well-adopted Comments tag (if you edit the comments on Windows, it'll show up under XPComments). You can pull them out with exiftool, and using -j renders output as json. If you want cross-platform support, auto-install of exiftool, better parsed results, and typescript typings, you can use https://github.com/photostructure/exiftool-vendored.js (which I extracted from PhotoStructure and open-sourced).