Add components/splitters section.

[bwinton]

As seen between panels, to let them resize.

[caterinasworld]

I can add a components/splitters.md page with the component definition and brief usage info. I can add the page as a draft, using the draft: true flag.

[bwinton]

Ooh, marking it as a draft is a good idea. That should let our Content Strategy team know that they should review it...