Change XDG defaults on Windows to use Windows spec

[kirawi]

Ref helix-editor/helix#6747

When the environment variables aren't set, they should use the Windows location instead. This is how most XDG implementations handle fallback on Windows, such as glib.

[utkarshgupta137]

I don't think it's a good idea to change the existing Xdg struct for Windows, because some tools might want to use the proper XDG definitions. The question is do we want to add a new struct to this crate for Mac & Windows or would the fallback from dev end suffice?
Maybe we could make the following function public: https://github.com/lunacookies/etcetera/blob/master/src/base_strategy/xdg.rs#L160?
WDYT?

[kirawi]

I'm not sure what would be the preferred solution, so I'll ask the other Helix maintainers.

[utkarshgupta137]

I think I would prefer making that function public so it is easier for all devs to mix & match strategies as they require. XdgWindows or XdgApple would just be a special case of that function.
In case you weren't aware, you could also implement the traits for your own struct & use that everywhere. It is especially helpful if you're changing the default paths & want a fallback solution in a single place in your workspace.
I'm also interested in using Helix, so let me know in case you need any help with helix-editor/helix#2135 or similar functionality.

[kirawi]

After speaking with one of the maintainers, your suggestion would work for Helix.

[utkarshgupta137]

Would you be fine with copying this function or do you really really want it to be in this library? From my perspective, this function actually doesn't have anything to do with this crate & one could pass any unrelated variables to it.

[kirawi]

Yep we can copy this function.