Hoist lefthook and stylelint to root

What does this MR do?

Hoists lefthook and stylelint to the root.

This may be easier to review commit-by-commit.

Part of #2034 (closed)

Commits

Hoist lefthook to root

Part of #2034 (closed)

Hoist stylelint to root

Part of #2034 (closed)

Move yarn-deduplicate check to pre-commit

It's fast enough, so why not?

Screenshots or screen recordings

N/A

Integrations

• GitLab: mr_url
• CustomersDot: mr_url
• Duo UI: mr_url
• Status Page: mr_url
• Docs: mr_url
• Switchboard: mr_url

Does this MR meet the acceptance criteria?

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Conformity

• The “What does this MR do?” section in the MR description is filled out, explaining the reasons for and scope of the proposed changes, per “Say why not just what”.
  • For example, if the MR is focused on usage guidelines, addressing accessibility challenges could be added in a separate MR.
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Components

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• If the MR changes a component's API, integration MR(s) have been opened (see integrations above).

Documentation

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Accessibility

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