New json version

Spine 3.7 is a bit outdated by now, and  no longer works with the most current runtime for unity, so I decided to update the .json file with a newer export. I'm also keeping the old version around however, in case someone needs it. They are now numbered to indicate which version of Spine they come from.

v37 is exported from Spine Version 3.7.91

v38 is exported from Spine version 3.8.84