The index of the spec had some very loose, incomplete content, a

leftover from when there was just the Sections page.
That has now been moved into a new Introduction page, and has been

expanded upon considerably. This page has an overview of DiffX, a Scope

section explaining what DiffX is trying to address and trying not to do,

more information on file extensions and expectations, and a brief

summary of the general file format.
The index page no longer has freeform text, but it does have some

information about the spec itself (version, copyright, and Last Updated

date).
The front of the docs package also now shows an example and links to

examples, helping tie that all together.

Built the docs. Checked for build errors, spelling errors, and bad

links.