docs: Fixes swapped logic for readonly function bindings

[ghost]

Read-only bindings should have the SET value assigned to null, not the GET.

e.g. this:
<input type="checkbox" bind:indeterminate={null, () => true} />

...fails, while this:

<input type="checkbox" bind:indeterminate={() => true, null} />

...works as expected.
(note: ts doesn't love this, prefers: <input type="checkbox" bind:indeterminate={() => true, () => null} />)

Question: should I also add explicit wording for bind:indeterminate since it no longer works without explicitly defining a getter/setter:

let status = 'pending'
<input type="checkbox" bind:indeterminate={(staus === 'pending')} />`
// or
<input type="checkbox" bind:indeterminate={(satus === 'pending') ? true : false} />

Fail. Rather:

<input type="checkbox" bind:indeterminate={() => true, null} />

...appears to be the only way this binding currently works in Svelte5.

Alternatively, should support for indeterminate={true} be a feat: ticket?

Repl (duplicated below):
https://svelte.dev/playground/1e48fd6b1c8a46b8aba20a37545a0cd8?version=5.19.6

(edits:clarity and repl inclusion)

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[Conduitry]

The first bind function is for taking a value from elsewhere in your app and applying it to this element. The second bind function is for taking a value from this element and applying it elsewhere in your app. The latter is correct for things like width/height bindings.

The names get and set are a bit confusing, especially since set is what you should be using for what we're calling 'read-only bindings'. I'm not sure how to make this less confusing.

This would be separate from whatever you're experiencing with bind:indeterminate. Do you have complete REPLs of what you're trying to achieve? There could well be a bug or a valid feature request here.

[ghost]

Ah! I interpreted the get/set detail incorrectly...it just happened to play directly into how I was attempting it.

https://svelte.dev/playground/1e48fd6b1c8a46b8aba20a37545a0cd8?version=5.19.6

Un-commenting the first two will fail.

edit: The first example may be unintended behavior, but I believe the second and third examples might simply benefit from an additional line or two on function bindings docs.

Indeterminate would be a good counter-example to dimensions, to add that clarity you've given me w/r/t the direction get/set operates in.