feat(markdown): add HTML-based table of contents

apps/client/src/widgets/sidebar/RightPanelContainer.tsx

@@ -75,7 +75,7 @@ function useItems(rightPaneVisible: boolean, widgetsByParent: WidgetsByParent) {
     const definitions: RightPanelWidgetDefinition[] = [
         {
             el: <TableOfContents />,
-            enabled: (noteType === "text" || noteType === "doc" || isPdf),
+            enabled: (noteType === "text" || noteType === "doc" || isPdf || !!note?.isMarkdown()),
         },
         {
             el: <PdfPages />,

apps/client/src/widgets/sidebar/TableOfContents.tsx

@@ -39,6 +39,7 @@ export default function TableOfContents() {
             {((noteType === "text" && isReadOnly) || (noteType === "doc")) && <ReadOnlyTextTableOfContents />}
             {noteType === "text" && !isReadOnly && <EditableTextTableOfContents />}
             {noteType === "file" && noteMime === "application/pdf" && <PdfTableOfContents />}
+            {note?.isMarkdown() && <ReadOnlyTextTableOfContents />}
         </RightPanelWidget>
     );
 }