Editor action `spawn-multi-cursor`.
Run it from the command palette or a key binding via the action id `spawn_multi_cursor`.
It is dispatched by `App::run_action("spawn_multi_cursor")` and, for editing actions, backed
by `Editor::spawn_multi_cursor` in `editor_core`. See `crates/vix-editor-core/spec/index.md` for the full
catalog.