Enforce trailing comma in JS on multiline (#30002)

To keep blame info accurate and to avoid [changes like
this](https://github.com/go-gitea/gitea/pull/29977/files#diff-c3422631a14edbe1e508c4b22f0c718db318be08a6e889427802f9b6165d88d6R359),
it's good to always have a trailing comma, so let's enforce it in JS.

This rule is completely automatically fixable with `make lint-js-fix`
and that's what I did here.

web_src/js/features/contextpopup.js

@@ -37,7 +37,7 @@ export function attachRefIssueContextPopup(refIssues) {
       interactiveBorder: 5,
       onShow: () => {
         el.firstChild.dispatchEvent(new CustomEvent('ce-load-context-popup', {detail: {owner, repo, index}}));
-      }
+      },
     });
   }
 }