Update design repo

[mjamescompton]

Summary

Update the design repo to latest version and include latest ttn-footer and include the cookie-banner.

References https://github.com/TheThingsNetwork/lorawan-devices/issues/372

Screenshots

Changes

• Update ttui assets
• Include cookie banner and js script
• Update ttn-footer import

Checklist

• [ ] Scope: The referenced issue is addressed, there are no unrelated changes.
• [ ] Run Locally: Verified that the docs build using make server, posted screenshots, verified external links.
• [ ] Style Guidelines: Documentation obeys style guidelines in CONTRIBUTING.
• [ ] Commits: Commit messages follow guidelines in CONTRIBUTING, there are no fixup commits left.