description notation should be title

[spring-raining]

Overview

The guidance of create-book requires us an input of description, however, the actual configuration name is title. It's better there is set as title.

[MurakamiShinyu]

If we change description to title we should also modify the default templates to use title. e.g., title: '{{name}}' should be changed to title: '{{title}}' in

create-book/templates/default/vivliostyle.config.js

Line 2 in ac6e65d

title: '{{name}}', // populated into `manifest.json`, default to `title` of the first entry or `name` in `package.json`.