Encoding equal to null should be established. Please take a look how spsave uploads documents.
Hello, How does the process of adding multiple list items work in sppp with sharepoint 2013? I get a batch error when adding multiple items using the official documentation
SPPP is not related to the API. It's a project generator/starter and a set of project automation tasks. Regarding the API question, batch API was not supported in SP 2013. The way to go is Promise.all instead.