feat(wm): add visual feedback for preselection

This commit adds visual feedback in the form of a ghost tile for
preselections made by the preselect-direction command.

A container with the id "PRESELECT" will be added to the workspace, and
replaced when the next manage-able window is spawned.

A new command, cancel-preselect, has been added to remove both the
preselection index and the ghost tile if the user changes their mind.

docs/cli/cancel-preselect.md

@@ -0,0 +1,12 @@
+# cancel-preselect
+
+```
+Cancel a workspace preselect set by the preselect-direction command, if one exists
+
+Usage: komorebic.exe cancel-preselect
+
+Options:
+  -h, --help
+          Print help
+
+```