feat: Update default menu placement to "auto"

[csandman]

This PR implements a change I've been meaning to make for a while. The menuPlacement prop determines where the select menu is placed depending on available screen space:

menuPlacement

Default placement of the menu in relation to the control. 'auto' will flip when there isn't enough space below the control.

One of<
  "bottom",
  "auto",
  "top"
>

— https://react-select.com/props#:~:text=menuPlacement

By default, the menu will always stay on the bottom (essentially meaning the prop defaults to "bottom"). However, the default behavior for the Chakra menus and popovers is to flip to the top if there isn't enough vertical space.

So I finally decided to make the executive decision to default this prop to "auto" to reflect that behavior, after having set it manually in so many of my own projects. This is actually already the case in chakra-react-select@6, but I wanted to update v5 to match. Here's what the behavior looks like:

Screen.Recording.2026-01-09.at.5.21.33.PM.mov

---

It is always possible to go back to the default behavior of react-select by passing the prop menuPlacement="bottom", so this isn't really a breaking change.

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📊 Package size report   0.3%↑

File	Before	After
dist/index.js	32.5 kB	0.7%↑32.8 kB
dist/index.mjs	30.9 kB	0.7%↑31.2 kB
Total (Includes all files)	155.1 kB	0.3%↑155.5 kB
Tarball size	31.1 kB	0.5%↑31.2 kB

Unchanged files

File	Size
dist/index.d.mts	20.0 kB
dist/index.d.ts	20.0 kB
LICENSE.md	1.1 kB
package.json	3.1 kB
README.md	47.5 kB

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

[csandman]

I added this prop also to match v6. I don't believe it does anything anyway, because this package uses all custom components, but it could prevent react-select from passing around unused styles. It doesn't hurt in either case.