Add Dependabot config

[mkernohanbc]

This PR adds new Dependabot config to give us a more structured approach to managing updates to the dependencies for design-system-react-components and design-tokens.

It configures Dependabot to perform a weekly scan for new versions of dependencies.

It applies two conditions:

• Only open PRs for minor/patch versions, ignore major versions (we handle these manually)
• Wait 7 days after a new version has released before opening a PR (as a defense against supply-chain attacks)

[Copilot]

Pull request overview

Adds a repository-level Dependabot configuration to standardize dependency update automation for the design system packages, aligning dependency maintenance with a predictable cadence and guardrails.

Changes:

• Introduces .github/dependabot.yml to enable weekly npm dependency scans for packages/react-components and packages/design-tokens.
• Configures Dependabot to ignore semver-major updates and apply a 7-day delay before opening update PRs.

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[ty2k]

Right on! 👍 👍