refactor(multiple-subtitles): [PKG-MULTI-SUB-04] expose compatible runtime type entry

refactor/fixtures/consumers/multiple-subtitles-export-alternatives.ts

@@ -0,0 +1,7 @@
+import type { Factory } from 'artplayer-plugin-multiple-subtitles'
+
+declare const replacement: Factory
+const required: Factory & { default: Factory } = replacement
+const optional: Factory & { default?: Factory } = replacement
+optional.default({ subtitles: [] })
+void required