fix(clipboard): add support for notion and github-flavored markdown checklist formats

- detect `to-do-list` (Notion) and `task-list` (GitHub MD) classes as checklist containers
- handle notion `<div class="checkbox-on/off">` as checkbox indicator in list items
- update README to document newly recognized HTML tags for checklist input

src/shared/components/BlockEditor/inline/clipboard.js

@@ -255,17 +255,28 @@ function hasBlockDescendant(el) {
 }
 
 function parseList(listEl, ordered, out) {
-  const isChecklist = listEl.hasAttribute('data-checklist');
+  // Détection « liste de cases à cocher » : data-checklist (export interne),
+  // ou class="to-do-list" (Notion), ou class contenant "task-list" (GitHub-flavored markdown).
+  const listClass = listEl.getAttribute('class') || '';
+  const isChecklist =
+    listEl.hasAttribute('data-checklist') ||
+    /\b(to-do-list|task-list|checklist)\b/i.test(listClass);
   for (const li of listEl.children) {
     if (li.tagName !== 'LI') continue;
-    // Détection checkbox (héritée du data-checklist OU d'un <input type=checkbox>
-    // dans le <li>, à la Markdown task list).
-    const checkbox = li.querySelector(':scope > input[type="checkbox"]');
+    // Détection checkbox au niveau item :
+    //  - <input type="checkbox"> direct child (GitHub task list, export interne)
+    //  - <div class="checkbox"> direct child (Notion : checkbox-on / checkbox-off)
+    const inputCb = li.querySelector(':scope > input[type="checkbox"]');
+    const divCb = li.querySelector(':scope > div.checkbox, :scope > div[class*="checkbox"]');
+    const checkbox = inputCb || divCb;
     const isChecklistItem = isChecklist || !!checkbox;
     let checked = false;
-    if (checkbox) {
-      checked = checkbox.checked || checkbox.hasAttribute('checked');
-      checkbox.remove();
+    if (inputCb) {
+      checked = inputCb.checked || inputCb.hasAttribute('checked');
+      inputCb.remove();
+    } else if (divCb) {
+      checked = /checkbox-on/.test(divCb.getAttribute('class') || '');
+      divCb.remove();
     }
 
     // Si le <li> contient lui-même des sous-listes, on émet d'abord un