Tests should run against prod build

[mktcode]

https://github.com/stamp-labs/stamp/blob/3c00957b63d4e061227dbe77628aa6de80668be5/package.json#L12

yarn dev starts nodemon and compiles on the fly, using ts-node. Instead build / start should be used, to .

In this case, we test without type-checking, if I'm not missing something, and on deployment we could still run into compile errors.

This workflow has been moved to this repo and needs adjustment, to add the build step. I guess you could also chain it together in the yarn test command.