Feat/add buffer support

[abdelkd]

This Pull-Request adds support for using Buffer inside of uploadFile function instead of having file to be on local disk. It can be used for example to process a form request and upload immediately instead of saving it on local and then uploading it.

[jimmywarting]

Thank you for this, this is the kind of smart thinking i like the most!
A package should assume as little about the system it runs on as much as possible.
I sometimes think it's bad that some application assumes it have access to some basic I/O operations when it could in fact run on multiple possible environment, like NodeJS, Bun, Deno, Browsers, Web Workers etc, it can be so sandboxed as much as possible. I might want to operate on the sandboxed file system in the browsers own storage.

a package should basically work as a stdin and stdout only and learn from the onion architecture

One small flaw in this PR is that you used node:Buffer instead of plain Uint8Array or ArrayBuffer instead. I'm not a huge fan of NodeJS specific things. it pollutes the env in other runtimes.

Another suggestion is to instead use Blob instead of buffer/uint8array/arraybuffer. a blob dose not necessary have to hold all data in memory and can be streamed instead. NodeJS, Bun and browser can back up the content of the file from a location on the disc. see eg: https://nodejs.org/api/fs.html#fsopenasblobpath-options