Fallback to `attrib` for `read-only` files on Windows

[past-gen]

Description

With sudo being completely out of the picture on Windows, we currently have a scenario where Micro successfully detects the file's state, but then inevitably fails when it comes to saving changes:

Trying to apply attrib -r automatically, and only then throw an error, in case of insufficient permissions, would be a more considerate approach in my opinion.

---

Alternatively/Optionally, a corresponding option in settings to control this behavior, with options:

• auto: makes the file writeable permanently when saved for the first time
• prompt: same as for Quit with unsaved changes
• preserve: respects the initial read-only state and restores it when saved

[JoeKar]

Somehow relates to #3541.

I assume this only helps for files which have the read-only option set, but not for those the user has absolutely no write permission for. So at the end this might help for a small percentage of files, but not for files for which only the administrator or someone else has write permission.

[past-gen]

I assume this only helps for files which have the read-only option set, but not for those the user has absolutely no write permission for.

Yes, that. Not talking about administrative rights here at all, sudo was mentioned as it appears in both, on-launch warning and on-save error.

Just thought that, since Micro does half the work already by detecting the file's current state, it'd be convenient to have the appropriate handling behavior builtin, so the user doesn't have to use a shell command every time or bind it from a plugin somewhere.

Like so done in SublimeText, for example: