Add Windows ARM64 native release for microsoft/git

[HarryGwinnell]

In a similar vein to #565, it would be great to have an ARM64 native version of Git. We consume microsoft/git and VFS for Git as part of our build process, and we're experimenting with using ARM64 hardware as part of our dev loop. Neither currently have a Windows ARM64 native edition

[dscho]

Not even Git for Windows has native ARM64 support, yet here is already a request to support it in microsoft/git... 😆