SIMULATION-ERRATA.md

As found by @tmcintos, the single-input flip-flop circuit described in Book IV on pages 68-69 seems to oscillate in the simulator, and not work:

https://minivac.greg.technology/simulator/#wires=5%2B%2F5H%206G%2F6F%205H%2F6H%205C%2F6C%205G%2F5F%206C%2F6-%206H%2F6Y%206X%2F5L%205K%2F6F%205N%2F6E%206Z%2F6L%206K%2F5E%206N%2F5F%206G%2F6A%206B%2F6-

It might be a simulator issue (we'd need a real device to test it/see how it actually behaves!) - for the time being, adding it here until we can know for sure.

Related discussion: #7

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