chore: fix get-container util ts def

Author: zombieJ

src/utils/get-container.ts

@@ -1,7 +1,11 @@
+export type GetContainer = () => HTMLElement
+
 export function resolveContainer(
-  getContainer: HTMLElement | (() => HTMLElement) | undefined | null
+  getContainer: HTMLElement | GetContainer | undefined | null
 ) {
   const container =
-    typeof getContainer === 'function' ? getContainer() : getContainer
+    typeof getContainer === 'function'
+      ? (getContainer as GetContainer)()
+      : getContainer
   return container || document.body
 }