Updated site following transition to OpenHW Foundation

Starting web content: https://docs.google.com/document/d/1CsrgA_wr4LADbndPRudlcbpVVEhQJUm-LnrQGeti7rk/edit?usp=sharing

Design: https://xd.adobe.com/view/18c1c086-758b-421b-87eb-e278a97b887d-4d92/ Maira will provide the assets from https://gitlab.eclipse.org/eclipsefdn/marketing/-/issues/2694

Code for membership form: code snippet can be found in this issue: https://github.com/openhwgroup/openhwgroup.org/issues/728

Note: there is a lot of additional content still under discussion in a separate document but we would like to get this site started while we work out the details.