fix: Fix automatic sort of Composite items in fixed containers

[EricRibeiro]

Closes #2

How to test?

Check generated CodeSandbox: https://codesandbox.io/s/cold-rain-fkr5b

Does this PR introduce breaking changes?

No

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Latest deployment of this branch, based on commit 905a747:

Sandbox	Source
Reakit	Configuration
cold-rain-fkr5b	Issue #2

[RonanFelipe]

Thanks for working on this @EricRibeiro! I'll take a look at it this weekend (hopefully).

[github-actions]

Size Change: 0 B

Total Size: 257 kB

ℹ️ View Unchanged

Filename	Size	Change
packages/reakit-playground/dist/reakit-playground.min.js	187 kB	0 B
packages/reakit-system-bootstrap/dist/reakit-system-bootstrap.min.js	19.1 kB	0 B
packages/reakit-system-palette/dist/reakit-system-palette.min.js	8.85 kB	0 B
packages/reakit-system/dist/reakit-system.min.js	2.45 kB	0 B
packages/reakit-utils/dist/reakit-utils.min.js	3.46 kB	0 B
packages/reakit/dist/reakit.min.js	36 kB	0 B

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[mairieli]

I'm also hitting this issue on a regular basis, it can be quite jarring on a long page – thanks for taking on the fix!