fix(thumbnail): [PKG-TOOL-THUMB-04] supply public types and installed module entries

test/types/thumbnail-source.ts

@@ -0,0 +1,8 @@
+import type Definition from 'artplayer-tool-thumbnail'
+import Implementation from '../../packages/artplayer-tool-thumbnail/src'
+
+const constructor: typeof Definition = Implementation
+const RuntimeConstructor: typeof Implementation = constructor
+const value: Definition = new RuntimeConstructor({ fileInput: document.createElement('input') })
+value.on('custom', (count: number) => count.toFixed())
+void value