Operation request: JavaScript deobfuscator

### Summary

An operation, or series of operations, to help in the deobfuscation of JavaScript code. Obfuscated JavaScript is becoming more and more common in malware samples, so some utilities to help deobfuscate it would be useful.

Please post ideas below.

The issue names no files, tests, or entry points and requests ideas rather than a defined change. Start by establishing the intended deobfuscation operations and acceptance criteria with maintainers; the work is done only once a concrete scope and verification approach are agreed.

Written by the indexing model from the issue text.