Create SDDS project contribution guide

Work is happening here:

https://www.drupal.org/community-initiatives/starshot-demo-design-system... →

This needs review now.

Assigning to Jacob for review.

Kristen Pol → credited jacobadeutsch → .

Jacob read through and didn't find anything obvious to update here. I'll leave this open for a day or two for others to take a look.

Kristen Pol → credited sea2709 → .

Reviewed by @sea2709 and all good. Thanks to you both!

Automatically closed - issue fixed for 2 weeks with no activity.