No Windows arm64 build

[ssbarnea]

On https://github.com/direnv/direnv/releases page there is no windows arm64 build and that is going to become quite popular soon.

Other:

• You don't need an arm64 Windows machine to build it, cross compile works.
• If you have an arm64 machine (M1), you can get https://www.microsoft.com/en-us/software-download/windowsinsiderpreviewARM64 and even re-use your existing Win10 license with it if you want to activate it, there is no difference.