refactor(layouts): add darwin feature gate and expand win32 feature gate

This commit builds on the newly introduced komorebi-layouts crate to
make it suitable for wholesale adoption in komorebi for Mac.

komorebi-layouts/Cargo.toml

@@ -15,7 +15,12 @@ tracing = { workspace = true }
 # Optional dependencies
 schemars = { workspace = true, optional = true }
 windows = { workspace = true, optional = true }
+objc2-core-foundation = { version = "0.3", default-features = false, features = [
+  "std",
+  "CFCGTypes",
+], optional = true }
 
 [features]
 schemars = ["dep:schemars"]
 win32 = ["dep:windows"]
+darwin = ["dep:objc2-core-foundation"]