feat: add arm64-simulator toolchain

[okwasniewski]

Hey,

As Apple is now shifting towards ARM Macs, I've added toolchain for ARM iossimulator.

Tested it by building Draco xcframework for ARM (iphoneos) + x86 + arm64 (simulator)

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[FrankGalligan]

Hi @okwasniewski Any plans to sign the CLA?