feat: better parse error message

[baszalmstra]

Changed the error message for parsing platforms to also include available values:

'foo' is not a known platform.

changed to:

'foo' is not a known platform. Valid platforms are 'noarch', 'linux-32', 'linux-64', 'linux-aarch64', 'linux-armv6l', 'linux-armv7l', 'linux-ppc64le', 'linux-ppc64', 'linux-s390x', 'linux-riscv32', 'linux-riscv64', 'osx-64', 'osx-arm64', 'win-32', 'win-64', 'win-arm64', 'emscripten-32'

[wolfv]

I still think we should have the option for completely custom platform values (they should follow the {platform}-{arch} schema though.