chore: Refactor upload placeholder (#5898)

shared/editor/lib/multiplayer.ts

@@ -0,0 +1,15 @@
+import { ySyncPluginKey } from "@getoutline/y-prosemirror";
+import { Transaction } from "prosemirror-state";
+
+/**
+ * Checks if a transaction is a remote transaction
+ *
+ * @param tr The Prosemirror transaction
+ * @returns true if the transaction is a remote transaction
+ */
+export function isRemoteTransaction(tr: Transaction): boolean {
+  const meta = tr.getMeta(ySyncPluginKey);
+
+  // This logic seems to be flipped? But it's correct.
+  return !!meta?.isChangeOrigin;
+}