added swiftlint warnings to appear in xcode

[charliescheer]

Fix

I keep creating linting errors on my recent PRs because Xcode does some things by default that the linter doesn't like. It was bugging me.... so I updated the project build settings to run and show SwiftLint errors in the project when building SNMac.

quality of life improvement for me.

Test

1. Open any swift file in SNMac and add a few extra lines in the middle somewhere.
2. Build the app and confirm that you see linting errors

Review

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Release

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[jleandroperez]

Thank you for doing this!!