feat(sync): attach local folders to existing My files folders

docs/CLI.md

@@ -79,6 +79,7 @@ commands are for scripts and for cases where the mount is not available.
 
 | Command | Description |
 |---|---|
+| `pdfs sync attach PATH --to REMOTE` | Merge a real local folder with an existing My files folder, keeping both versions on initial conflicts. |
 | `pdfs sync add PATH` | Back up a local folder under this computer and keep it in sync. |
 | `pdfs sync list` | List synced folders with their IDs and state. |
 | `pdfs sync rm ID [--delete-remote]` | Stop syncing. Local files stay; `--delete-remote` also removes the copy on Proton Drive. |