style lists based on their attributes

(aside: this illustrates why I want to share CSS between webview and PDF/EPUB)

Notes:

- blockish numbered lists (`<ol>`) can use all of the `list-style-type:` attributes
- blockish bulleted lists (`<ul>`) can use **some** of the `list-style-type:` attributes but some have to be "emulated"
- inline bulleted lists are `<span>` with classes (browsers do not like `<ol>` inside a `<p>`) and have to be "emulated"
- inline numbered lists are `<span>` with classes and have to be "emulated" with counters

Tasks:

- [x] implement `@data-list-type`, `@data-bullet-style`, and `@data-number-style`
- [x] implement `@data-item-sep`: for inline lists it is a `;` by default and for blockish lists it is nothing by default
- [x] discuss `@data-mark-prefix` and `@data-mark-suffix`