feat(wm): add cmd to specify work area offsets

This commit adds a new komorebic command to specify offsets for work
areas to be applied across all monitors. The areas covered by these
offsets will be excluded from the tiling area, and can be used for
custom task bars, Rainmeter desktop widgets etc.

When setting an offset at the top, the same offset will need to be
applied to the bottom to ensure that the tiling area is not pushed off
of the screen, but this is not necessary when applying an offset to the
bottom as the top of the work area will never go lower than 0.

resolve #46

komorebi-core/src/lib.rs

@@ -72,6 +72,7 @@ pub enum SocketMessage {
     ReloadConfiguration,
     WatchConfiguration(bool),
     InvisibleBorders(Rect),
+    WorkAreaOffset(Rect),
     WorkspaceRule(ApplicationIdentifier, String, usize, usize),
     FloatRule(ApplicationIdentifier, String),
     ManageRule(ApplicationIdentifier, String),