doc: clarify that fs.exists() may return false for existing symlink · nodejs/node@73860ac

* `callback` {Function}

* `exists` {boolean}

Test whether or not the given path exists by checking with the file system.

Test whether or not the element at the given `path` exists by checking with the file system.

Then call the `callback` argument with either true or false:

```mjs

has only one boolean parameter. This is one reason `fs.access()` is recommended

instead of `fs.exists()`.

If `path` is a symbolic link, it is followed. Thus, if `path` exists but points

to a non-existent element, the callback will receive the value `false`.

Using `fs.exists()` to check for the existence of a file before calling

`fs.open()`, `fs.readFile()`, or `fs.writeFile()` is not recommended. Doing

so introduces a race condition, since other processes may change the file's