Added activeIndex class to repeater

[Blackbaud-AlexKingman]

Addresses #43

Style should be similar to vertical tabs:
https://developer.blackbaud.com/skyux/components/vertical-tabs#demo

This class will be used to show which item is active when using in conjunction with split view component.

Docs update needed. Issue filed here: blackbaud/skyux2-docs#575

[Blackbaud-AlexKingman]

☝️ Matches vertical tabs:
https://github.com/blackbaud/skyux-tabs/blob/master/src/app/public/modules/vertical-tabset/vertical-tab.component.scss#L28

[codecov]

Codecov Report

Merging #51 into master will increase coverage by 0.04%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master      #51      +/-   ##
==========================================
+ Coverage   99.52%   99.57%   +0.04%     
==========================================
  Files          24       24              
  Lines         424      470      +46     
  Branches       41       46       +5     
==========================================
+ Hits          422      468      +46     
  Misses          2        2

Impacted Files	Coverage Δ
...rc/app/public/modules/repeater/repeater.service.ts	100% <100%> (ø)	⬆️
...public/modules/repeater/repeater-item.component.ts	100% <100%> (ø)	⬆️
.../app/public/modules/repeater/repeater.component.ts	100% <100%> (ø)	⬆️

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[Blackbaud-ToddRoberts]

styling looks correct to me

[Blackbaud-SteveBrush]

Thanks so much for the detailed comments; helps a ton when reviewing.

I know the visual demo only allows for one active item at a time, but it's possible to make more than one item active if the consumer wishes. I'm thinking we'd like to avoid that kind of behavior and force the active state to only one of the items?

What if you put an activeItemIndex on the <sky-repeater> component instead?

[Blackbaud-AlexKingman]

Updated to go off activeIndex property on sky-repeater instead of each individual repeater item. This is based on the same patter tabs is using.

[Blackbaud-SteveBrush]

One quick comment.

[Blackbaud-SteveBrush]

I think there are a few structural changes that are needed. The repeater items should handle their own registration (and unregistration) with the service in their ngOnInit and ngOnDestroy. If we need to talk it through offline, let me know!

[Blackbaud-SteveBrush]

Much better. Great work!