Example on how to extract `ArrayBuffer` from files#9

Hi! First of all thanks for maintaining this repo, I am looking forward to build some nice tools in reMarkable and this library looks promising. I am trying to upload an `epub` via the `uploadEpub` method. When submitting a file, the request is successful, but when trying to open the submitted file on my reMarkable device, I get an error message (it complains of being unable to open the file). My gut feeling is that I am not passing the right `ArrayBuffer` to the request. I am trying to find examples in the docs of how to get a buffer from a file via Node.js, but I have not found anything. This is how I am currently trying to read the file in my project: ```ts async function readFileAsArrayBuffer (filePath: string): Promise<ArrayBuffer> { const data = await fs.readFile(filePath) return data.buffer } ``` The returning values are what I am passing to `await api.uploadEpub("name", buffer);`. Is there something I am doing wrong when extracting the body?