Batch delete issue and improve tippy opts (#25253)

1. Add "batch delete" button for selected issues, close #22273
2. Address the review in
https://github.com/go-gitea/gitea/pull/25219#discussion_r1229266083

web_src/js/features/comp/ConfirmModal.js

@@ -0,0 +1,30 @@
+import $ from 'jquery';
+import {svg} from '../../svg.js';
+import {htmlEscape} from 'escape-goat';
+
+const {i18n} = window.config;
+
+export async function confirmModal(opts = {content: '', buttonColor: 'green'}) {
+  return new Promise((resolve) => {
+    const $modal = $(`
+<div class="ui g-modal-confirm modal">
+  <div class="content">${htmlEscape(opts.content)}</div>
+  <div class="actions">
+    <button class="ui basic cancel button">${svg('octicon-x')} ${i18n.modal_cancel}</button>
+    <button class="ui ${opts.buttonColor || 'green'} ok button">${svg('octicon-check')} ${i18n.modal_confirm}</button>
+  </div>
+</div>
+`);
+
+    $modal.appendTo(document.body);
+    $modal.modal({
+      onApprove() {
+        resolve(true);
+      },
+      onHidden() {
+        $modal.remove();
+        resolve(false);
+      },
+    }).modal('show');
+  });
+}