fix: Include TS type declarations.

[kinyoklion]

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• [x] I have added test coverage for new or changed functionality No added functionality.
• [x] I have followed the repository's pull request submission guidelines
• [x] I have validated my changes against all supported platform versions

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[shortcut-integration[bot]]

This pull request has been linked to Shortcut Story #192432: Issues with typescript with openfeature-node-server.

[kinyoklion]

Tested using published 0.3.0-alpha.1 package.