Selectmenu: Add disabled default options to product selection demo

[fnagel]

As @jzaefferer proposed, I've added a "please choose" option with selected and disabled attribute.

[jzaefferer]

Looks good to me. I'll let someone else take a look as well, hopefully we're not on the wrong track.

[fnagel]

Yeah, not sure if the empty initial state is what we want.

[scottgonzalez]

What is the intent of this change?

[scottgonzalez]

@jzaefferer We're wondering why we explicitly want to demo this behavior since it's just standard <select> behavior.

[jzaefferer]

We didn't have a single demo or even visual test that was using this standard <select> behaviour. I think its worth showing that it still works for selectmenu.

[scottgonzalez]

Can we find a better demo for it? A product selector that starts with no preview at all isn't great UX.

[tjvantoll]

Agreed that this is bad UX. What if we just added a fourth select to the main demo with a more common use case for this functionality—maybe salutation?

[scottgonzalez]

That sounds good to me.

I'll close this and someone can send a new PR with a different change.