Split index.js to separate files (#17315)

* split `index.js` to separate files

* tune clipboard

* fix promise

* fix document

* remove intermediate empty file

* fix async event listener

* use `export function` instead of `export {}`, add more comments

Co-authored-by: Lunny Xiao <xiaolunwen@gmail.com>
Co-authored-by: 6543 <6543@obermui.de>

web_src/js/components/RepoActivityTopAuthors.vue

@@ -101,10 +101,9 @@ const sfc = {
   }
 };
 
-function initRepoActivityTopAuthorsChart() {
+export function initRepoActivityTopAuthorsChart() {
   initVueApp('#repo-activity-top-authors-chart', sfc);
 }
 
-export default sfc;
-export {initRepoActivityTopAuthorsChart};
+export default sfc; // this line is necessary to activate the IDE's Vue plugin
 </script>