Add corpus files for json-differential fuzz target

[jeffcharles]

Description of the change

Adds a series of corpus files generated after fuzzing the json-differential target for a while and running cargo +nightly fuzz cmin json-differential.

Why am I making this change?

We want to add a corpus to make fuzzing more efficient.

Checklist

• [x] I've updated the relevant CHANGELOG files if necessary. Changes to javy-cli and javy-plugin do not require updating CHANGELOG files.
• [x] I've updated the relevant crate versions if necessary. Versioning policy for library crates
• [x] I've updated documentation including crate documentation if necessary.