File.CreateSymbolicLink functionality is missing (Added in .net6.0)

[davidrogers090]

Is your feature request related to a problem? Please describe.
I'd like to be able to use the File.CreateSymbolicLink and Directory.CreateSymbolicLink functionality in a testable way.

Describe the solution you'd like
The IFile.CreateSymbolicLink and IDirectory.CreateSymbolicLink and the default implementations available for use.

Describe alternatives you've considered
I could use the old way to create symbolic links, but this is messy and difficult to test.
I could invoke cmd.exe mklink, but this is not cross-platform and has serious security concerns.

Additional context
Related to #789.

[fgreinacher]

This makes a lot of sense, contributions welcome 👍

[davidrogers090]

I've begun working on this. I should be able to do a PR soon.

[fgreinacher]

Thanks @davidrogers090! Feel free to ping me anytime for support/feedback!

[vbreuss]

I think this is now implemented with #965...