Add support for ObjC/C Package

[Kyle-Ye]

Add support for ObjC/C Package

Checklist

• If possible, I've reproduced the issue using the main branch of this package.
• This issue hasn't been addressed in an existing GitHub issue.

Expected behavior

Generate docc preview successfully.

Actual behavior

error: target 'XX' is not a Swift source module

Steps to Reproduce

1. Init an empty C Package and add Documentation Catalog(XX.docc foloder).
2. Add Swift-DocC-Plugin depenedency
3. Run swift package --disable-sandbox preview-documentation --target XX

Swift-DocC Plugin Version Information

Swift-DocC plugin version: 1.1.0
Swift Compiler version:

swift-driver version: 1.75.2 Apple Swift version 5.8 (swiftlang-5.8.0.124.2 clang-1403.0.22.11.100)
Target: arm64-apple-macosx13.0

[Kyle-Ye]

We've already got clang support for ObjectiveC symbol graph generation. But this method need multi commands to achieve. It would be nice if Swift DocC Plugin could do them for us.

https://forums.swift.org/t/clang-support-for-objective-c-symbol-graph-generation/57689

[Kyle-Ye]

I just summarized Swift-docc-plugin's support for ObjC & Swift language with a repository.

For anyone interested, you can check it here https://github.com/Kyle-Ye/swift-docc-plugin-mix-demo