chore: adding .xcode.env.local to $.gitignore (#759)

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### Summary

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Adding `.xcode.env.local` to the `.gitignore`

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packages/create-react-native-library/templates/common/$.gitignore

@@ -28,6 +28,7 @@ DerivedData
 *.ipa
 *.xcuserstate
 project.xcworkspace
+**/.xcode.env.local
 
 # Android/IJ
 #