[Docs] make it clearer that onedrive, googledrive, etc, are supported via the builtin fs

[ecstrema]

I almost abandoned using OneKeePass simply because I did not find out immediately how to open a file stored on onedrive.

Actually, I had no idea that there was a virtual filesystem on these platforms.

I would recommend making it clearer somewhere. Either in the app, or adding some instructions somewhere for how to use onekeepass with storage providers.

[jeyasankar]

Thanks @ecstrema ,

I will add some documents on this