feat(wm): lock

Containers can be locked since the model came in, and a locked container keeps
its index while others are inserted, removed or swapped around it; nothing could
lock one. `komorebic toggle-lock` locks the focused container, or unlocks it,
and the `LockMonitorWorkspaceContainer` and `UnlockMonitorWorkspaceContainer`
messages lock and unlock a container by the index of its monitor, its workspace
and itself, for a program such as a status bar.

The vm-commands sweep locks and unlocks a container.

docs/cli/toggle-lock.md

@@ -0,0 +1,10 @@
+```text
+Toggle a lock for the focused container, ensuring it will not be displaced by any new windows
+
+Usage: toggle-lock
+
+Options:
+  -h, --help
+          Print help
+
+```