updates to unknown values

[mattgarrish]

I ended mostly rewriting the intro to the hazards section to try and better explain all the possibilities we now have. I also updated the example and added two new ones to show some different permutations rather than have text explanations.

Otherwise, I had to update the lists of which properties must not / should not be used together, as they needed to account for the unknown values.

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Preview | Diff

[mattgarrish]

@clapierre there are links to a preview and diff in the first comment. Are they not working for you?

What do you think about re-ordering the values a bit? Right now we group them in quasi-alphabetic order, but placing all the positive/negative/unknown values indidvidually together:

flashing
noFlashingHazard
unknownFlashingHazard
motionSimulation
noMotionSimulationHazard
unknownMotionSimulationHazard
sound
noSoundHazard
unknownSoundHazard
unknown
none

It might be easier to follow if we separate each group of positive, negative, unknown values like this:

flashing
motionSimulation
sound
none
noFlashingHazard
noMotionSimulationHazard
noSoundHazard
unknown
unknownFlashingHazard
unknownMotionSimulationHazard
unknownSoundHazard

[clapierre]

Oh missed that first comment with the preview. works great.

Yeah I also wondered about that. I think you may be right lets reorder them.

[mattgarrish]

I ended up going one step further and made it more like the accessibility features by adding grouping sections, so it's now:

Hazard terms
 - flashing
 - motionSimulation
 - sound
No hazard terms
 - none
 - noFlashingHazard
 - noMotionSimulationHazard
 - noSoundHazard
Unknown hazard terms
 - unknown
 - unknownFlashingHazard
 - unknownMotionSimulationHazard
 - unknownSoundHazard

I'll merge this into your pull request so we can view all the changes together.