getting file path from Deno.FsFile

[teidesu]

given a Deno.FsFile, there's currently no way to determine path to it's underlying file system file. i suggest adding some kind of api that would allow that, something along

const file = await Deno.open('file.txt')
assert(file.path == "file.txt")

similar to how it's possible in Node.js:

const file = fs.createReadStream('file.txt')
console.log(file.path) // "file.txt"

this is mostly just a developer experience improvement, as it would allow not having to store path to file separately and just reference it from .path. and it would also allow library developers to accept the handles returned by Deno.open and derive file name directly from them