Allow `encodeArrayKey` function to receive plain key name as first argument

[CJ42]

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• bug report
• feature request
• question about the decisions made in the repository
• question about how to use this project

Summary

The function encodeArrayKey currently behaves incorrectly and does not throw an error when the input is the data key name.
Instead, it expects a hex string to be passed but this is not enforced by the typings. See screenshots below:

Other information (e.g. detailed explanation, stack traces, related issues, suggestions how to fix, links for us to have context, eg. StackOverflow, personal fork, etc.)