Update XCSharedData Writable conformance to include WorkspaceSettings

[dayton-bobbitt]

Resolves #738

Short description 📝

Update XCSharedData Writable conformance so that WorkspaceSettings are wrriten.

Solution 📦

There was already a pattern defined for writing XCSharedData properties (schemes and breakpoints), and so I followed the same pattern to write the workspaceSettings property.

Implementation 👩‍💻👨‍💻

Detail in a checklist the steps that you took to implement the PR.

• Write a test case in XcodeProjTests that fails if XcodeProj.write doesn’t write all expected files
• Run the test and see that it fails
• Update XCSharedData Writable conformance to write WorkspaceSettings
• Run XcodeProjTests again and see that it passes

[kwridan]

Thanks @dayton-bobbitt

[dayton-bobbitt]

Thanks @kwridan! Is there anyone else in particular we need to review this change before it can be merged?

[kwridan]

Thanks @brentleyjones for the quick review!