fix(parallax): add position properties to layer

[kindoflew]

Why

Found this bug while making the new demo for testing (I didn't even set up cypress yet 😅):

If more than 2 layers are sticky on the same page, their positions may be suddenly shifted down a page before becoming sticky when scrolled to a second time (depending on their order in the HTML). Description might not be totally clear, but you can see what I mean here: https://codesandbox.io/s/nifty-night-j6xdm?file=/src/App.tsx.

Obviously, I had to discover this the day after 9.2.0 released.

What

Instead of having conditional position properties like this:

[layer.horizontal ? 'left' : 'top']: 0

All four are now listed explicitly (top: 0, bottom: 0, etc..). This has no effect on regular layers.

In the future when the inset property has more support we can switch it to that so it looks a little cleaner, but that's a nitpick really. (Also, by that time, overflow: clip will hopefully be better supported and we can just use that instead and none of this will matter anyways.)

Checklist

• Documentation updated: N/A
• Demo added: N/A
• Ready to be merged

[codesandbox-ci]

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spring-card	Configuration
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spring-flip-card	Configuration
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spring-cards-stack	Configuration
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spring-simple-transition	Configuration
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dark-surf-sgy56	PR

[joshuaellis]

Good spot! I'll release this now. I'm thinking of adding the changesets bot like in leva so contributors will be prompted to make a changeset 🤔