Make read on a FsFile without { read: true } error message clearer

[CyanChanges]

Open a file without specify { read: true }

import { toText } from 'jsr:@std/streams'
const file = await Deno.open('log-1.json', { append: true })
const lines = await toText(file.readable)

Result in error:

error: Uncaught (in promise) Error: Bad file descriptor (os error 9)
    at async Object.pull (ext:deno_web/06_streams.js:941:27)

In this case, instead of Bad file descriptor (os error 9) , FsFile is not readable should be more clear.

This is just an example.
I can't just use Deno.readTextFile(...) instead.