#7419382 Sites Dashboard: Skeleton for new dashboard

Proposed Changes

This addresses the first “create a skeleton” task in #65163. It does a bit more than the acceptance criteria, but I figured it was worth committing the table even though it’s not finished.

It’s a biggish commit, but I’ve tried to split the commits into more readable chunks if that helps.

The parts that are important for the acceptance criteria:

• Header elements have the correct spacing
• Mobile layout works
• Heading typography is correct
• Links to the signup flow
• Anything else you see mentioned in #65163

Some issues that I don’t think block this PR:

• I’m currently importing Calypso code into the components package. Discussing refactoring things so that’s not necessary. p1656917133483219/1656482582.511659-slack-C02DQP0FP
• After clicking “New Sites” the back button in the top-left of the site creation flow doesn’t return the user back to the dashboard. I’ve created a task for that #65183

Testing Instructions

• Head to calypso.localhost:3000/sites-dashboard to try it out
• Use the “New site” button
• Try a phone layout

Fixes #65163