adding .xcworkspace to gitignore

[jlmitch5]

This folder is created by xcode when one of the examples is run. Probably makes since to include this in the .gitignore as it doesn't make sense to keep the compiled native code under source control.

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[frantic]

Why? We don't have any workspaces in the repo yet, but I think when we do we would want to check them in

[ide]

@frantic is right, workspaces should be checked in. Adding xcuserdata makes sense though. Here's a template for ideas:

.DS_Store
*/build/*
*.pbxuser
!default.pbxuser
*.mode1v3
!default.mode1v3
*.mode2v3
!default.mode2v3
*.perspectivev3
!default.perspectivev3
xcuserdata
profile
*.moved-aside
DerivedData
.idea/
*.hmap
*.xccheckout