Add Xcode auto-generated XCSchemes to .gitignore

[rdas-ditto]

Excluded the auto-generated XCSchemes from Swift Package Manager under .swiftpm/xcode/xcshareddata/xcschemes/ by adding them to .gitignore.

This change prevents unnecessary files from being tracked in the repository, as these schemes are auto-generated by Xcode and can be safely ignored to keep the version control system clean.

[bplattenburg]

Should we also be removing the existing tracked files there?

[rdas-ditto]

Good catch, I've updated the .gitignore, and also removed the existing tracked files (xcscheme, and also Package.resolved)

[rdas-ditto]

This is ready to review, and merge.