Add zeek/zeek-version.h include

[awelzel]

🗣 Description

I'd like to use this plugin for builtin-plugin integration testing within the Zeek CI pipeline (as an example of an external plugin using binpac). Due to zeek/zeek#2806 with the latest master version this requires an explicit zeek/zeek-version.h include.

That include is good practice anyway, so it'd be nice if that could be merged.

Reference zeek/zeek#2847.

💭 Motivation and context

See description.

🧪 Testing

• Compile testing when build into Zeek using ./configure --include-plugins=...

✅ Pre-approval checklist

• [x] This PR has an informative and human-readable title.
• [x] Changes are limited to a single goal - eschew scope creep!
• [x] All future TODOs are captured in issues, which are referenced in code comments.
• [ ] All relevant type-of-change labels have been added.
• [ ] I have read the CONTRIBUTING document.
• [ ] These code changes follow cisagov code standards.
• [ ] All relevant repo and/or project documentation has been updated to reflect the changes in this PR.
• [ ] Tests have been added and/or modified to cover the changes in this PR.
• [ ] All new and existing tests pass.

✅ Pre-merge checklist

• [ ] Revert dependencies to default branches.
• [ ] Finalize version.

✅ Post-merge checklist

• [ ] Create a release.