[select] Add `multiple` prop

[atomiks]

Closes https://github.com/mui/base-ui/issues/1956

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vite-css-base-ui-example

npm i https://pkg.pr.new/@base-ui-components/react@2173

commit: 136877c

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@base-ui-components/react	🔺+1.47KB(+0.48%)	🔺+480B(+0.49%)

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[ej-shafran]

Hey y'all - is there any update on this? What needs to be done to get this merged?

If needed, I can pick this up and help fix the relevant issues... Would really love to have this feature as it's very relevant for basically every project where I use a Select...

[atomiks]

Note on hidden <select> vs. hidden <input>s:

From what I can tell the hidden <select> requires all possible <option>s to be available upfront (the browser autofill test fails in particular if not), which would make the items prop required and also introduce some cost of creating all the <option> elements. The hidden inputs on the other hand don't have this issue