feat: update blocks with new brand

[thomasguillot]

All Submissions:

• Have you followed the Newspack Contributing guideline?
• Does your code follow the WordPress' coding standards and VIP Go coding standards?
• Have you checked to ensure there aren't other open Pull Requests for the same update/change?

Changes proposed in this Pull Request:

Replaces the Newspack logo/icon with our new logo
Updated the primary colour (and removed block icons colours)
Replaced pattern image placeholder with something more generic

How to test the changes in this Pull Request:

1. Switch to this branch
2. Make sure patterns still work
3. Check the block inserter, we should have the new logo and the new icon colours

Other information:

• Have you added an explanation of what your changes do and why you'd like us to include them?
• Have you written new tests for your changes, as applicable?
• Have you successfully ran tests with your changes locally?