feat(lambda): Add handler for upcoming Lambda URI

[rhamilt]

Problem

The Lambda team plans to add a URI handler to act as an entrypoint to the toolkit from a URL. This will be fully available in an upcoming toolkit release, but customers who don't have that version will not get the benefit of the handler.

Solution

Add a handler ahead of time telling customers to update to the latest version. This way, customers who have an older version with this change will be notified that the functionality they are trying to use is in a newer version. This should help customers from becoming confused when they open a link and an older version says it is not handled.

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• Treat all work as PUBLIC. Private feature/x branches will not be squash-merged at release time.
• Your code changes must meet the guidelines in CONTRIBUTING.md.
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[github-actions]

• This pull request modifies code in src/* but no tests were added/updated.
  • Confirm whether tests should be added or ensure the PR description explains why tests are not required.
• This pull request implements a feat or fix, so it must include a changelog entry (unless the fix is for an unreleased feature). Review the changelog guidelines.
  • Note: beta or "experiment" features that have active users should announce fixes in the changelog.
  • If this is not a feature or fix, use an appropriate type from the title guidelines. For example, telemetry-only changes should use the telemetry type.

[justinmk3]

👍 thanks for re-using the existing module and patterns.