Charter: Add Digital Publishing Interest Group to section 4.1

WCAG,
The DPUB IG would like us to add a reference to the DPUB IG in the Coordination section, under 4.1 (http://www.w3.org/2016/11/proposed-ag-charter#coordination).

Their charter already indicates that they will be coordinating with WAI groups, so it seems appropriate for this to be explicitly bi-directional.  Do people agree that this change is agreeable?

Thanks,
AWK

Andrew Kirkpatrick
Group Product Manager, Standards and Accessibility
Adobe

akirkpat@adobe.com
http://twitter.com/awkawk