Add a consolidated What's New changelog view

[thisisdano]

Summary

Add consolidated changelog. Add a view to the What's New page so design system users know what's changed across the design system.

There've been many changes to the design system in the last couple weeks, and we've recently added content change alerts to content affected by recent executive orders and policy guidance.

It's important that design system users know how the design system is changing. We have changelogs on individual pages, but there's currently no way to see all the changes in a single view.

This PR adds a consolidated changelog to our What's New page so design system users can better keep up to date with these changes. This new view will show the last 250 changes to the design system.

Related issue

Closes #1829

Preview links

Preview →

How to test

• Visit the What's New page and check for the new view at the after the two content cards. Check that it's an accurate log of the most recent changes to the design system.
• Check for consistent use of affectsContent (component content) and affectsPageContent (page content)
• Check documentation in changelog README
• Check for distinctions between page content and links (link updates only)

[amyleadem]

Update: I added a related issue in the PR description since this issue should close #1829. @thisisdano let me know if that is not appropriate.

[annepetersen]

LGTM

[amyleadem]

Note

I am in the process of prepping some additional changes to this PR in #3118 so that it fits the structure from the prototype in PR #3094.