Behaviors.Animations.md file needs work

[michael-hawker]

While cleaning up the docs I noticed this doc is a mismatch of a couple of topics. Part of it should go in the animations package for AnimationSet and the rest should be in the Behaviors package.

I've fixed it for the import to the docs in MicrosoftDocs/CommunityToolkit#312

But we need to fix it in the repo here for the sample app and for auto-exporting later. Since the filenames map to the doc names, it was a weird mapping already to begin with.

Just filing this issue for tracking/

[michael-hawker]

In general we need to enable the sample app to link to other documents within the repo somehow, and we need to validate these links are valid...