Improve user docs for writing hooks (#1057)
Improve user docs for writing hooks (#1057)

This PR adds documentation based on my experience writing a hook for
the first time.

This adds a new section to hooks.rst called "Writing hooks" that
includes topics related to writing pre/post-generate hooks:

- exit status (restructured from a note)
- current working directory of a script when its run
- highlight that Cookiecutter evaluates jinja syntax in the scripts
hackebrot/cookiecutter,audreyr/cookiecutter,pjbull/cookiecutter,michaeljoseph/cookiecutter,audreyr/cookiecutter,hackebrot/cookiecutter,luzfcb/cookiecutter,michaeljoseph/cookiecutter,pjbull/cookiecutter,luzfcb/cookiecutter