refs https://github.com/TryGhost/Team/issues/870
- currently, a handful of packages in this repo generate type
declarations when building
- we're aiming to go more in the direction of better inline jsdoc, and
we want to clean up all generated files and use of external types
- this commit removes the `typescript` dependency, removes the pretest
commands that run the builds, and cleans up anywhere where we
configure types
