feat(cli): add cycle-empty-workspace cmd

This commit adds a variation of the cycle-workspace command which will
attempt to focus the next empty workspace in the given direction (with
the usual wraparound). If there are no empty workspaces available, this
command will do nothing.

docs/cli/cycle-empty-workspace.md

@@ -0,0 +1,16 @@
+# cycle-empty-workspace
+
+```
+Focus the next empty workspace in the given cycle direction (if one exists)
+
+Usage: komorebic.exe cycle-empty-workspace <CYCLE_DIRECTION>
+
+Arguments:
+  <CYCLE_DIRECTION>
+          [possible values: previous, next]
+
+Options:
+  -h, --help
+          Print help
+
+```