Create mockup for Working Group application page

To facilitate new changes to the portal to enable organizations to apply to a working group in a self-serve fashion, a new page will be needed in the portal. This page will capture a working group, the membership level, and the contact that will be used to sign the user. To keep the look-and-feel consistent, we will need assistance from the Marketing/Design team in providing a design mock-up for this page. Discussed previously in the monthly membership meeting, we can likely reuse a lot of the look and feel for the "Working Group" slide of the membership application as it captures the same data.

I've set a due date of end of March for final design, though we should aim for earlier for a chance to have revisions and reviews!

/cc @sgiacomoni2as /cc @mkokabi