Add `middleware-e2e-encryption` middleware example

[jpwilliams]

Summary

Adds an example middleware, middleware-e2e-encryption.

Checklist

• [ ] Added a docs PR that references this PR N/A
• [ ] Added unit/integration tests N/A
• [x] Added changesets if applicable

[changeset-bot[bot]]

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Latest commit: 8d13ad542e87080ac381341ab139e7711569ddf8

Merging this PR will not cause a version bump for any packages. If these changes should not result in a new version, you're good to go. If these changes should result in a version bump, you need to add a changeset.

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