fix(vanilla): use case with refed proxies

[dai-shi]

ref() is usually used for non plain objects, but what if we use it for valtio proxy objects.
It might be more intuitive to cut the structure with a ref'ed proxy.

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Name	Status	Preview	Updated
valtio	✅ Ready (Inspect)	Visit Preview	Jan 11, 2023 at 3:12PM (UTC)

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[github-actions]

Size Change: +39 B (0%)

Total Size: 50.7 kB

Filename	Size	Change
dist/esm/vanilla.js	2.27 kB	+7 B (0%)
dist/system/vanilla.development.js	2.4 kB	+8 B (0%)
dist/system/vanilla.production.js	1.45 kB	+6 B (0%)
dist/umd/vanilla.development.js	2.59 kB	+7 B (0%)
dist/umd/vanilla.production.js	1.53 kB	+3 B (0%)
dist/vanilla.js	2.47 kB	+8 B (0%)

ℹ️ View Unchanged

Filename	Size
dist/esm/index.js	746 B
dist/esm/macro.js	629 B
dist/esm/macro/vite.js	743 B
dist/esm/utils.js	4.18 kB
dist/index.js	767 B
dist/macro.js	870 B
dist/macro/vite.js	1.03 kB
dist/system/index.development.js	915 B
dist/system/index.production.js	523 B
dist/system/macro.development.js	737 B
dist/system/macro.production.js	555 B
dist/system/macro/vite.development.js	851 B
dist/system/macro/vite.production.js	660 B
dist/system/utils.development.js	4.4 kB
dist/system/utils.production.js	2.92 kB
dist/umd/index.development.js	909 B
dist/umd/index.production.js	624 B
dist/umd/macro.development.js	1.01 kB
dist/umd/macro.production.js	727 B
dist/umd/macro/vite.development.js	1.19 kB
dist/umd/macro/vite.production.js	882 B
dist/umd/utils.development.js	4.66 kB
dist/umd/utils.production.js	3 kB
dist/utils.js	4.51 kB

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[dai-shi]

As #626 will hit a new minor version, let's put this into it too. I'm still skeptical about the use case, but it doesn't harm. (only a little size increase)