- Move the styles for these components out of `annotation.scss` and into
   separate files to follow project conventions.

 - Refactor style names to use BEM-ish naming conventions

There are some exceptions here because annotation body and quote
elements have styles that are customized when the annotation is a reply
or when the annotation card is hovered. Those customizations are still
in annotation.scss because they need to match both the parent and child
components.