feat: Amazon EventBridge Extractor

[ka1319]

Summary of Changes

Added a new extractor for fetching schema metadata from AWS EventBridge schema registries.

Tests

Added databuilder/tests/unit/extractor/test_eventbridge_extractor.py for testing the new extractor.

Documentation

Updated README.md and databuilder/README.md to reflect the addition of the new extractor.

CheckList

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• PR adds unit tests, updates existing unit tests, OR documents why no test additions or modifications are needed.
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  • All the public functions and the classes in the PR contain docstrings that explain what it does

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs.

[feng-tao]

thanks @kahrabian for the contribution!

[boring-cyborg]

Awesome work, congrats on your first merged pull request!