Refactor repo legacy (#32404)

Only move code, no unnecessary logic change. (There are many problems in
old code, but changing them is not in this PR's scope)

Co-authored-by: Giteabot <teabot@gitea.io>

web_src/js/features/repo-milestone.ts

@@ -0,0 +1,11 @@
+import $ from 'jquery';
+
+export function initRepoMilestone() {
+  // Milestones
+  if ($('.repository.new.milestone').length > 0) {
+    $('#clear-date').on('click', () => {
+      $('#deadline').val('');
+      return false;
+    });
+  }
+}