Allow file descriptor arguments to fs/readFile

[dbohdan]

Currently fs/readFile expects the path argument to be a string.

> cat test.cljs
(require '["fs"])

(fs/readFile 0
             "utf8"
             (fn [err data] (js/console.log data)))

> lumo test.cljs < test.cljs
The "path" argument must be of type string. Received type number
         assertPath (path.cljs:39:11)
         Object.resolve (path.cljs:168:7)
         getKey (C:NaN:37)
         readFile (C:NaN:172)
         Object.<anonymous> (C:NaN:3)
         Module._compile (internal/modules/cjs/loader.cljs:689:30)
         (Object.It)
         (Object.lumo.repl.caching_node_eval)
         (NO_SOURCE_FILE <embedded>:6265:9)
         z (NO_SOURCE_FILE <embedded>:6266:22)

However, per the official Node.js documentation path may be an integer representing a file descriptor. This is convenient, e.g., for reading the whole of the standard input.

> cat test.js
const fs = require('fs');

fs.readFile(0, 'utf8', (err, data) => console.log(data));

> node test.js < test.js
const fs = require('fs');

fs.readFile(0, 'utf8', (err, data) => console.log(data));

The workaround of "/dev/stdin" does not work on Windows.