Added text to conformance icon description pages

Hello,

Following a request for similar information for the WCAG 1.0
conformance pages, I added the following text to the
ATAG 1.0 conformance icon description pages [1], [2], [3]:

<BLOCKQUOTE>
The Authoring Tool Accessibility Guidelines 1.0 provides guidelines
for Web authoring tool developers. Its purpose is two-fold: to assist
developers in designing authoring tools that produce accessible Web
content and to assist developers in creating an accessible authoring
interface. Conformance to these Guidelines will make the Web more
accessible to users with disabilities and will benefit all users.
</BLOCKQUOTE>

 - Ian

[1] http://www.w3.org/WAI/ATAG10A-Conformance.html
[2] http://www.w3.org/WAI/ATAG10AA-Conformance.html
[3] http://www.w3.org/WAI/ATAG10AAA-Conformance.html

-- 
Ian Jacobs (jacobs@w3.org)   http://www.w3.org/People/Jacobs
Tel:                         +1 831 429-8586
Cell:                        +1 917 450-8783