typing challenge prototype

src/lib/serial/connection.ts

@@ -19,6 +19,8 @@ export const layout = writable<CharaLayout>([[], [], []])
 
 export const unsavedChanges = writable(0)
 
+export const highlightActions: Writable<number[]> = writable([])
+
 export const syncStatus: Writable<"done" | "error" | "downloading" | "uploading"> = writable("done")
 
 let device: CharaDevice // @hmr:keep