Summary:
we want to use react-cookie-banner to match what we will eventually use for our marketing site.
most of the code here is just styling, which we dont have a set mockup for, so feel free to nitpick the CSS

Test Plan:
screenshots:
{F101557}

{F101558}
updated zindex:
{F101792}

Reviewers: nick, zasgar, nserrino, #engineering

Reviewed By: nserrino, #engineering

Differential Revision: https://phab.corp.pixielabs.ai/D6704

GitOrigin-RevId: f46804369136e3ae923a470aa56d700ea6bf81ac