Ready TOC and TOCController for indigo replacement

[musangowope]

• create custom event itemRendered that is emit with item data when la-toc-item is rendered
• add sb story demoing itemRendered
• Write basic test for itemRendered
• update item prop of la-toc-item to possibly have selected it data shaped i.e.

{
  title: "Lorem",
  children: [],
  selected: false
}

use selected to conditionally append CSS class active to of la-toc-item .content__action

[longhotsummer]

I think we can close this?

[musangowope]

yep