CSS @keyframes Best Practice

In `src/App.css` we have the `@keyframes spin` rule:

``` css
@keyframes spin {
  from { transform: rotate(0deg); }
  to { transform: rotate(360deg); }
}
```

Wouldn't best to rename `spin` to `App-logo-spin`? That way we teach newcomers to avoid "CSS globals" for everything.

I mean, `@keyframes spin` is a good candidate to be added in many component's CSS file.
