Docs: Enhancement proposal

[louismaximepiton]

Description

Apply the same display for stacks and flex examples.

Motivation & Context

Following the #37899. I'm less sure about this one, this is why I made 2 different PRs, but it's still to harmonize the doc.

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-37900--twbs-bootstrap.netlify.app/docs/5.3/helpers/stacks
• https://deploy-preview-37900--twbs-bootstrap.netlify.app/docs/5.3/helpers/vertical-rule#with-stacks

Related issues

NA

[mdo]

Thanks for all these PRs!