Add a CI Check to ensure .node-version Parity w/nix

[abhillman]

tl;dr: Adds a script and a CI check to ensure .node-version is at parity with the nix-managed node --version.

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Context: https://github.com/malloydata/malloy/pull/1314#issuecomment-1709166424

Why: Added as a courtesy for @whscullin, @mtoy-googly-moogly; note that only certain node managers read .node-version (source)

[whscullin]

/gcbrun