Add "Windows only" to readme

[msikma]

I think it would be useful to add a note to the readme and stating this is for Windows only.

I'm on Mac and I had just installed the package and had already started writing some code, and then I opened the wiki to look for more documentation and happened to see that it uses WinAPI. 😅

The Github "about" text in the sidebar does say it's for Windows, but this text does not show up on npm unfortunately.

[Strajk]

@msikma heya, any luck finding an alternative for macOS? is that even possible or is mac just "too sanboxed"?

[Cedo9999]

it is theoretically possible to get a a memory editor that works on macOS.