Document why DirExt::access on Windows doesn't use their faccess equivalent

I noticed that your Windows implementation of `DirExt::access` just tries opening the file.

I understand if [_access, _waccess, t_access](https://learn.microsoft.com/en-us/cpp/c-runtime-library/reference/access-waccess?view=msvc-170) or [_access_s, _waccess_s, _taccess_s](https://learn.microsoft.com/en-us/cpp/c-runtime-library/reference/access-s-waccess-s?view=msvc-170) from the Microsoft C Runtime impose additional dependencies you want to avoid, and that the Win32 API-native version's [overcomplicated credentials](https://blog.aaronballman.com/2011/08/how-to-check-access-rights/) blow up to six pages in the [faccess](https://github.com/Freaky/faccess/) crate's Windows implementation ([Link to the source file](https://github.com/Freaky/faccess/blob/master/src/lib.rs), MIT-licensed) once you address various edge cases.

However, I was unable to find any clear documentation for the rationale behind that. (Which I'm guessing is "auditing burden".)

Could that be improved, please?

首先定位 DirExt::access 的 Windows 实现，并阅读它当前如何通过打开文件来检查访问权限。将这种方式与链接的 Microsoft CRT APIs 和 faccess Windows 实现进行比较，然后记录项目采用该方式的理由，包括已确认的任何依赖项或审计方面的疑虑。完成标准是：在不更改实现的情况下，该理由对读者而言清晰明确。

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