refactor(thumbnail): [PKG-TOOL-THUMB-04] type runtime modules and retain emitter attribution

packages/artplayer-tool-thumbnail/src/utils.ts

@@ -0,0 +1,9 @@
+export function getFileName(name: string) {
+  const nameArray = name.split('.')
+  nameArray.pop()
+  return nameArray.join('.')
+}
+
+export function clamp(num: number, a: number, b: number) {
+  return Math.max(Math.min(num, Math.max(a, b)), Math.min(a, b))
+}