refactor(client): use public interface exclusively

This commit demotes the komorebi-core crate to a module (core) inside of
the komorebi lib, resulting in the komorebi-client crate lib becoming
the single public interface for programming in Rust against komorebi.

komorebic and komorebi-gui now consume komorebi-client exclusively as
the means for sending and receiving messages to and from komorebi, so
that anyone wishing to integrate with komorebi will have all of the same
functionality to them as I do.

komorebi/src/monitor.rs

@@ -12,7 +12,7 @@ use schemars::JsonSchema;
 use serde::Deserialize;
 use serde::Serialize;
 
-use komorebi_core::Rect;
+use crate::core::Rect;
 
 use crate::container::Container;
 use crate::ring::Ring;