Yuque backup utilities.
Copy config-template.json to anywhere and modify its content.
Note that the host field only accepts URLs that is not suffixed with /, or the URL parsing will fail. This may be fixed in the future.
Use yuque-squirrel -c <CONFIG_PATH> <PATH> to start the backup process.
The backup process is incremental, which means that it will only download new or updated documents.
This program is single-threaded, but it's async, so it should be fast enough, although with blocking filesystem operations.