Broadcast mouse activity (#1175)

* broadcast mouse activity

* move to same MOUSE_LOCATION event

* remove key up handler

* update tests

* Fix border

* refactor

* rename activity to button

Co-authored-by: Panayiotis Lipiridis <lipiridis@gmail.com>

src/appState.ts

@@ -26,6 +26,7 @@ export function getDefaultAppState(): AppState {
     scrollY: 0 as FlooredNumber,
     cursorX: 0,
     cursorY: 0,
+    cursorButton: "up",
     scrolledOutside: false,
     name: `excalidraw-${getDateTime()}`,
     isCollaborating: false,