fix: Re-add relative positioning to MenuList

[csandman]

This PR closes #352

There was an issue with the menu scrolling behavior using the arrow keys due to removed relative positioning on the MenuList component. You can see where it was removed in V6 here: https://github.com/csandman/chakra-react-select/pull/341/files#diff-282462b390ca3390d40b92e5bb7575995e675a710c8958176ffbae47e15a3411L116

This was most likely removed by mistake in an attempt to clean up as many style overrides as possible.

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commit: e92624b

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📊 Package size report   0.1%↑

File	Before	After
dist/index.js	31.0 kB	0.3%↑31.0 kB
dist/index.mjs	29.4 kB	0.3%↑29.5 kB
Total (Includes all files)	151.4 kB	0.1%↑151.5 kB
Tarball size	29.7 kB	0.3%↑29.8 kB

Unchanged files

File	Size
dist/index.d.mts	19.6 kB
dist/index.d.ts	19.6 kB
LICENSE.md	1.1 kB
package.json	3.0 kB
README.md	47.8 kB

_{🤖 This report was automatically generated by pkg-size-action}