Promisifying of fs may not be correct

The wrap function only deals with first two arguments of the original function's callback. This may not work properly for any function which give more than 2 args in their result callback like fs.read and fs.write. They produce 3 args in the result callbacks (err: NodeJS.ErrnoException, bytesRead: number, buffer: TBuffer)

https://github.com/bcoin-org/blgr/blob/master/lib/fs.js#L15

Start by reading lib/fs.js at line 15, focusing on the wrap function and how it handles callbacks from fs.read and fs.write. Check the callback results those functions provide, then verify that the promisified versions preserve all returned values rather than only the first two; done means those calls expose the complete callback result.

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