Support innerHTML in serialization recipe

I understand you don't want to support serialization in this project which makes sense. However, when experimenting with the example recipe I've noticed an issue when serializing the document after Preact mutates it. I end up with elements that have both innerHTML and childNodes[] defined. The innerHTML value seems to have not been cleaned up. I'm not sure where or why this is happening exactly. Any thoughts?

I've added innerHTML and void elements to my implementation here: https://gist.github.com/Stanback/3bb0b19b299668ce0e08922a8ab6876e

Start with the example serialization recipe and reproduce the case where Preact mutates the document, leaving both innerHTML and childNodes[] defined. Compare the serialized output with the gist implementation, focusing on innerHTML and void elements. Done means serialization no longer retains stale innerHTML after mutation.

Written by the indexing model from the issue text.