feat(#3511): add links to DS 2 docs

[bdfranck]

This PR makes the following changes to the DS 1 docs:

Notification banner changes

• Adds a site-wide notification that encourages teams to view DS 2 upgrade docs
• If a user dismisses the notification, it re-appears in the next session
• Removes the previous version control & LTS upgrade notifications

Individual page changes

• Adds a v2 link to component page header
• Adds a v2 link to example page header

Version menu changes

• Adds v2 link to both the React and Angular menus

The DS 2 docs changes: https://github.com/GovAlta/ui-components/pull/3554.

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[Spark450]

Overall looking good, would all these changes be deployed on the 31st along with the finalized links (e.g. the unbuilt "Migration guide" page)?

[bdfranck]

To do: Update the links with the final DS 2 docs URL.

[bdfranck]

I've converted this back to draft and blocked the related issue until we complete GovAlta/ui-components#3510.