Fix deprecation suggestion of select event handler types

[timothyis]

What's Changed

When I was updating from v8 -> v9 I came across the deprecation notice for the SelectSingleEventHandler, which gave me the deprecation notice before this PR. When using the suggestion, I was met with:

ts: Type '"single"' has no properties in common with type '{ mode?: Mode | undefined; required?: boolean | undefined; }'.

Implementing the change I've made on this PR made the warning disappear, though you can also do SelectHandler<{ required: true }> and I'm not sure if that's correct. So maybe a type change needs to be made also.

Type of Change

• Bug fix
• New feature
• Breaking change
• Documentation update

[rodgobbi]

Hi @timothyis

Thanks for the PR!

It's indeed a mistake of the docs, as the generic type for the SelectHandler type needs to extend { mode?: Mode | undefined; required?: boolean | undefined }.

Could you fix the linter in your changes?
So the CI passes and we can merge the changes.