Add consent banner to site

[travjenkins]

Issue

Fixes https://github.com/estuary/marketing-site/issues/250

Changes

• Add a consent bannd
• Have consent make call to Google Tag Manager

Tests / Screenshots

Consent banner when there are no cookies or changes to consent

Manage pop up for fine grained management

Cookie to allow management after making a selection

[github-actions[bot]]

Visit the preview URL for this PR (updated for commit 8343e0f):

https://estuary-marketing--pr252-travjenkins-feature-equefrf8.web.app

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[Brenosalv]

@travjenkins Just left two comments but the code lgtm.