Developing the Announcements pattern

[jlongshore]

Create the Announcement pattern based on the C4IP Tearsheet.

This will leverage the Carbon content switcher in the "Navigation" slot, which will allow the user to switch between this current release's tier 1 level features and ALL features listed in docs (historical).

The Navigation slot will also contain a custom Grid layout to accommodate the "View on docs" link.

The influencer will contain a bespoke "Table of contents" component which will watch the scrolled area with an intersection observer for updating the current element.

The content area will contain custom components to view features (including images and links)