Feature: add examples in block.json

[JoshuaHungDinh]

Resolves: [GIVE-2256

Description

This PR adds the example object to our blocks registered with block.json. This will allow a small preview to be generated while selecting the block from the left sidebar

https://developer.wordpress.org/block-editor/reference-guides/block-api/block-registration/#example-optional

Affects

• Campaign Blocks

Visuals

Example.previews.mov

Testing Instructions

• create a campaign and select edit campaign page.
• select the + symbol to open the left sidebar.
• hover over each new campaign block and see if an associated "example" image is shown above its description.

Pre-review Checklist

• Acceptance criteria satisfied and marked in related issue
• Relevant @unreleased tags included in DocBlocks
• Includes unit tests
• Reviewed by the designer (if follows a design)
• Self Review of code and UX completed

[jonwaldstein]

@JoshuaHungDinh I was hoping someone would update this haha thank you!!!