refactor(layouts): extract independent komorebi-layouts crate

This commit moves layout-related code into a new workspace crate
komorebi-layouts, with the intention of re-using it all in komorebi for
Mac instead of maintaining two separate implementations.

komorebi-layouts/src/layout.rs

@@ -0,0 +1,32 @@
+use serde::Deserialize;
+use serde::Serialize;
+
+use super::Arrangement;
+use super::CustomLayout;
+use super::DefaultLayout;
+use super::Direction;
+
+#[derive(Debug, Clone, Serialize, Deserialize, PartialEq)]
+#[cfg_attr(feature = "schemars", derive(schemars::JsonSchema))]
+pub enum Layout {
+    Default(DefaultLayout),
+    Custom(CustomLayout),
+}
+
+impl Layout {
+    #[must_use]
+    pub fn as_boxed_direction(&self) -> Box<dyn Direction> {
+        match self {
+            Layout::Default(layout) => Box::new(*layout),
+            Layout::Custom(layout) => Box::new(layout.clone()),
+        }
+    }
+
+    #[must_use]
+    pub fn as_boxed_arrangement(&self) -> Box<dyn Arrangement> {
+        match self {
+            Layout::Default(layout) => Box::new(*layout),
+            Layout::Custom(layout) => Box::new(layout.clone()),
+        }
+    }
+}