Add SDK values for node and unity-web

[bcherry]

We'd like to be able to distinguish these SDKs from their underlying implementations (Rust and JS).

I'm not sure if there is more I'm supposed to do for testing when submitting a protocol PR so lmk.

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[lukasIO]

@bcherry I'll merge this and cut a new release so we can start implementing this.

[bcherry]

@lukasIO thank you!