.gitignore: Ignore all json files as they are generated
.gitignore: Ignore all json files as they are generated

Signed-off-by: Andrei Gherzan <8dc7c09356db0b1762fb140617d7375c0a5a4131@resin.io>

resin-os/resin-beaglebone,resin-os/resin-beaglebone