Add verbosity setting

A standard assistive technology setting is verbosity, which controls how much information the software returns to the user about each element.

Verbosity is meant to reveal semantics that are usually visually conveyed so the user can know, for example, when a citation starts or ends. However, high verbosity can become annoying and disrupt the reading experience, so it needs to be user-controlled.

No files, tests, or entry points are named. Start by clarifying the expected user-controlled verbosity behavior and how citation boundaries should be exposed; done should include an agreed scope for the setting and its effect on the reading experience.

Written by the indexing model from the issue text.