Merge public ihasmail: folder reordering, full-screen composer, Dutch update

- Reorder folders by dragging, with special folders first (#402, #405).
- Open the composer full screen, as a setting (#401, #404).
- Dutch translation update (#403).

FEATURES.md stays deleted here, as in bb25355.

web/src/locales/es.ts

@@ -748,6 +748,7 @@ export const catalog: Catalog = {
     "Attachment reminder": "Aviso de adjunto",
     "Warn when the message mentions an attachment but none is attached.": "Avisar cuando el mensaje menciona un adjunto pero no hay ninguno.",
     "Spell check while typing": "Corrección ortográfica al escribir",
+    "Open the composer full screen": "Redactar mensajes a pantalla completa",
     "Confirm before deleting": "Confirmar antes de eliminar",
     "Show message snippets": "Mostrar un fragmento de los mensajes",
     "Preview the first line of each message in the list.": "Mostrar la primera línea de cada mensaje en la lista.",