[dpub] Sample EPUBWEB document

Attached is a sample EPUBWEB [1]  document using the W3C/TAG streaming
package format [2].

The file is provided as a straw-man, to facilitate discussion in the
Digital Publishing Interest Group.

Dave Cramer

[1] https://w3c.github.io/epubweb/
[2] http://w3ctag.github.io/packaging-on-the-web/