fix: move utility types out of .d.ts file to fix exported declaration files (#6315)

src/actions/shortcuts.ts

@@ -1,5 +1,6 @@
 import { isDarwin } from "../constants";
 import { t } from "../i18n";
+import { SubtypeOf } from "../utility-types";
 import { getShortcutKey } from "../utils";
 import { ActionName } from "./types";
 

src/actions/types.ts

@@ -6,6 +6,7 @@ import {
   ExcalidrawProps,
   BinaryFiles,
 } from "../types";
+import { MarkOptional } from "../utility-types";
 
 export type ActionSource = "ui" | "keyboard" | "contextMenu" | "api";