Fix typing: export the identified w/ declared type

Author: yhatt

src/index.d.ts

@@ -1,5 +1,6 @@
-export default {
+declare const htm: {
   bind<HResult>(
     h: (type: any, props: Record<string, any>, ...children: any[]) => HResult
   ): (strings: TemplateStringsArray, ...values: any[]) => HResult | HResult[];
 };
+export default htm;