Update brand.md

[manipinnaka1125]

Description
This pull request adds a Brand Colors section to the docs/5.3/about/brand/ page in Bootstrap's documentation. The new section provides users with an overview of the primary colors used in the Bootstrap framework, displayed with color swatches, hex codes, and brief usage descriptions for each color. This addition enhances the branding guidelines by making the brand's color palette readily accessible alongside existing logo and naming guidelines.

Motivation & Context
This change is intended to help users quickly identify and reference the primary colors associated with Bootstrap's brand. By adding the color palette to the brand guidelines, users can better align their designs with Bootstrap’s aesthetic, ensuring a consistent look and feel.

Type of changes
Bug fix (non-breaking change which fixes an issue)
New feature (non-breaking change which adds functionality)
Refactoring (non-breaking change)
Breaking change (fix or feature that would change existing functionality)
Checklist
I have read the contributing guidelines
My code follows the code style of the project (using npm run lint)
My change introduces changes to the documentation
I have updated the documentation accordingly
I have added tests to cover my changes
All new and existing tests passed
Live previews
https://deploy-preview-{your_pr_number}--twbs-bootstrap.netlify.app/
Related issues

This PR description provides a clear explanation of the changes and why they were made, and follows the structure outlined for Bootstrap's contribution guidelines. Be sure to replace {your_pr_number} in the live preview link with your actual pull request number.

Closes #40926

[julien-deramond]

Thanks for your contribution @manipinnaka1125
Could you please fix the build so that we can get a deployed version and check what you've done? You can run npm run docs locally.

[mdo]

These colors aren't specific to Bootstrap's brand, but the design system. No point in adding them IMO as the Customize section tackles this just fine.