Add image support to Pillar component

[danielguillan]

Summary

Adds support to include an image as part of the Pillar component.

List of notable changes:

• Added <Pillar.Image>.
• Updated interface guidelines and React docs.
• Updated the bottom margin of images to ensure consistency across Pillars and Cards.

Steps to test:

• Storybook
• Interface guidelines
• React docs

Supporting resources (related issues, external links, etc):

• Resolves [Feature request] Add image support to the Pillar component #836

Contributor checklist:

• All new and existing CI checks pass
• Tests prove that the feature works and covers both happy and unhappy paths
• Any drop in coverage, breaking changes or regressions have been documented above
• UI Changes contain new visual snapshots (generated by adding update snapshots label to the PR)
• All developer debugging and non-functional logging has been removed
• Related issues have been referenced in the PR description

Reviewer checklist:

• Check that pull request and proposed changes adhere to our contribution guidelines and code of conduct
• Check that tests prove the feature works and covers both happy and unhappy paths
• Check that there aren't other open Pull Requests for the same update/change

[changeset-bot]

🦋 Changeset detected

Latest commit: 688442f

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 6 packages

Name	Type
@primer/react-brand	Patch
@primer/brand-primitives	Patch
@primer/brand-e2e	Patch
@primer/brand-fonts	Patch
@primer/brand-config	Patch
@primer/brand-storybook	Patch

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[github-actions]

🟢 No design token changes found

[github-actions]

🟢 No visual differences found

Our visual comparison tests did not find any differences in the UI.

[natalie-iv]

@jesussandreas could you please take a look. we had that discussion in Slack around margin below the image. Would love to hear your perspective.