Split "About" page into two menu items

We should split the content on this page (https://sdv.eclipse.org/about/) into two page under the "About" menu.

The first page is "What is SDV" and the second is "About the Working Group". The content split can be found in this doc: https://docs.google.com/document/d/1kuSw_LJ00mTS8gkWi6AtXSG4eR16lFA_vUmNYZepRgY/edit?usp=sharing

Problem were solving: "About the working group" will have a second link to the charter (since we've heard it's hard to find on the homepage) and will give us a natural location to add meeting minute links.

@paulinagueorguieva @sgallian @dana please let me know if you have any concerns with this recommendation.