sketch.json? Why haven't I seen this before?

Today I was working at home on create.arduino.cc. I suspect my school is using an outdated version of the IDE, as the site has a lot more features. When I went and downloaded the sketch, inside the zip was a .json file. Was this requirement put in an update? I've never seen the on-board version create a json. Will I need to keep this file to use the sketch or can I discard it and simply use the main .ino file?

Really old topic indeed, but I have an answer for this and I guess it may help everyone stumbling on this is the future.

There is some documentation of the Arduino CLI referencing the sketch.json file: Redirecting

Arduino CLI and Arduino Web Editor use a file named sketch.json, located in the sketch root folder, to store sketch metadata.

Hope it helps!