Include the @types/jest dependency in the package.json for the unbox token project

[harshnambiar]

The first step after doing an aztec-cli unbox token is currently needing to do a yarn add @types/jest because it's a necessary dependency for yarn build to get through, but isn't present. This can be changed by including it in the package.json

[dan-aztec]

thanks @harshnambiar !