artiq: add dependency jsonschema
Support for resolution of https://github.com/m-labs/artiq/issues/1474
Co-authored-by: Stephan Maka <sm@m-labs.hk>
Reviewed-on: M-Labs/nix-scripts#38
Co-Authored-By: Astro <sm@m-labs.hk>
Co-Committed-By: Astro <sm@m-labs.hk>