Add Swift/Xcode icons

[uncenter]

Type

• File icon
• Folder icon

Context and associations

• .swiftformat (https://github.com/nicklockwood/SwiftFormat)
• *.xcsettings, *.xcworkspacedata
• *.xcodeproj/, *.xcworkspace/, xcshareddata/, xcschemes/ (directories all starting with xc basically)
• *.entitlements (https://developer.apple.com/documentation/bundleresources/entitlements, icon looks like:
  )

References

https://developer.apple.com/xcode/:

[kaascevich]

Perhaps we should also add icons for SwiftPM-specific files/directories, such as Package.swift, Package.resolved, .swiftpm, and .build (although that could probably just use the existing folder_dist icon)?

I'm no icon designer, but in Xcode:

• Package.swift uses a normal Swift icon, but with a tan color instead of the usual orange.
• Package.resolved simply uses a generic JSON icon (though we could probably do better... perhaps an icon with a lock badge in the vein of cargo-lock or ruby-gem-lock?).
• .swiftpm has no special icon, by virtue of not showing up in Xcode at all, but we could probably just use a folder icon with a Swift badge.