Fix #212 - Return correct properties and values for SWDMv4 trace functions

Triage

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This pull request:

[ ] Adds a new carbon estimation model to CO2.js
[ ] Adds new functionality to an existing model
[x] Fixes a bug with an existing model implementation
[ ] Add other new functionality to CO2.js
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[ ] Improves developer experience for contributors
[ ] Adds contributors to CO2.js
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This update ensures that the correct properties are returned when using either version 3 or version 4 of the Sustainable Web Design Model with the perByteTrace or perViewTrace functions. This helps deal with the fact that there are different properties that need to be returned depending on the version of the model that is used.

thegreenwebfoundation / co2.js