Please clarify how the target property works for Node

Looking at https://esbuild.github.io/getting-started/#bundling-for-node I can't find any explanation of how this property works or what the valid values are. I can put `'node100'` in that property and it will compile fine. This seems odd ([violation of POLS](https://medium.com/@julietasudjana/stop-doing-magic-embrace-pols-instead-f2fa95c3a7aa)) because I would not expect a non-existent version of Node to actually work. I would expect an error.

So an FAQ that explains how that value is processed would be helpful.

STR: take a config for node, replace the target (node20 etc) and replace with node100.

Expected: error because Node 100 does not exist.

Actual: compilation goes ahead anyway and ... decides what feature set to use based on some internal logic?

Start at the “Bundling for Node” section of the esbuild getting-started guide and review the target configuration behavior using the provided node20/node100 reproduction. Document the valid Node target values and explain how an unrecognized value such as node100 is processed; the guide should answer why compilation proceeds and what feature set is selected.

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