Add fkYAML 0.4.2

[matthias-giersch]

Adds fkYAML version 0.4.2 (https://github.com/fktn-k/fkYAML) to BCR.

[google-cla]

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[bazel-io]

Hello @bazelbuild/bcr-maintainers, modules without existing maintainers (fkyaml) have been updated in this PR.
Please review the changes. You can view a diff against the previous version in the "Generate module diff" check.

[gemini-code-assist]

Code Review

This pull request adds fkyaml version 0.4.2 to the Bazel Central Registry. The changes are well-structured and mostly follow the BCR guidelines. I've found one issue regarding the bazel_compatibility attribute missing in the overlay's MODULE.bazel file, which is recommended by the style guide. Please address this to ensure forward compatibility. Otherwise, the submission looks good.