Design is an important part of the Jenkins project, but right now we do not have page for it on the jenkins.io/participate page

Acceptance criteria:

• A new jenkins.io/participate/design page is created
• There are initial contents added to this page. E.g. see https://docs.google.com/presentation/d/1JHgVzWZAx95IsUAZp8OoyCQGGkrCjzUd7eblwd1Y-hA/edit#slide=id.g61fd74a45d_2_87 for ideas
• There is a new "Design" section added to to the "Contribute" section