feat(entries): add Copy value to the custom-field row menu

The inline copy button stays: copy is the frequent action and burying it costs a click every time. Unlike the old lock-versus-eye pair, two ways to copy are not confusable.

js/app.js

@@ -4318,6 +4318,14 @@ function buildCustomFieldRow(field, idx, rerender) {
         kebabMenu.classList.toggle('is-open');
     });
 
+    const copyItem = el('button', { class: 'kebab-item', type: 'button' }, 'Copy value');
+    copyItem.addEventListener('click', ev => {
+        ev.stopPropagation();
+        kebabMenu.classList.remove('is-open');
+        copyBtn.click();
+    });
+    kebabMenu.appendChild(copyItem);
+
     const secretItem = el('button', { class: 'kebab-item', type: 'button' });
     const paintSecretItem = () => {
         secretItem.textContent = field.is_secret ? 'Make public' : 'Store as secret';