Get this into the design review template

[torgo]

We need to come to consensus to add this to the design review template and add it.

[matatk]

Some movement on this :-); we are discussing in w3ctag/design-reviews#1088

[matatk]

We are about ready to make a PR for the HTML version of the form that I showed on a recent TAG call, but I'd like to check people are OK with my proposal in #6 first.