Update README with steps to run/build ISSIE on Apple Silicon

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Is your feature request related to a problem? Please describe.

The native (arm64) version of dotnet 6.0.403 panic to run dotnet fake build on apple silicon Mac, with error message:

Script is not valid:
        unknown (1,0)-(1,0): Error FS0193: The specified file name or path is too long, or a component of the specified path is too long.

There is an open issue in FAKE repo about this fsprojects/FAKE#2626.

Describe the solution you'd like

The workaround is to install x86_64 version of dotnet instead, and use Rosetta2 to run it.

By this way, the built ISSIE executable will still be arm64.

Extra

Personally highly recommend to use asdf to manage different versions (including different ISA targets) of runtimes (e.g. Node.js, dotnet) on Linux and macOS.