Docs: use 'added' page information to display a tag on top of the pages

[julien-deramond]

Description

In some of our Markdown files, we got an added information but apparently we never display that information:

bootstrap/site/content/docs/5.2/helpers/color-background.md

Lines 1 to 8 in 39bbca5

	---
	layout: docs
	title: Color & background
	description: Set a background color with contrasting foreground color.
	group: helpers
	toc: true
	added: "5.2"
	---

This PR suggests to use this information and to display it on top of the corresponding pages next to the "View on GitHub" button.

Motivation & Context

Bring more information to the users about the latest changes.

Type of changes

• New feature (non-breaking change which adds 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

Live previews

• Components > Placeholders
• Helpers > Color & background
• Helpers > Stacks
• Helpers > Vertical rule
• Layout > CSS Grid
• Utilities > Opacity