Add instructions on how to install a local version of the annotations repo

A common usecase is that a user needs to experiment with new commands and therefore needs to update annotations. Currently annotations are downloaded from PyPI and therefore it is hard to play with a local version of the library. We should add instructions on how to locally install and work with a local branch of annotations. Ideally, we could also add a script that helps with that (in addition to instructions).

Start by locating where the project currently documents or performs the PyPI download of annotations. Add instructions for installing and using a local branch, and determine whether a helper script is appropriate; done means a user can follow the documented workflow to experiment with updated annotations.

Written by the indexing model from the issue text.