docs(ngClass): add docs regarding animation for `ngClassEven` and `ngClassOdd`

Previously, the documentation has no information regarding using
`ngAnimate` together with the `ngClassEven` and `ngClassOdd` directives.

This commit adds the same docs used by the `ngClass` directive to the
`ngClassEven` and `ngClassOdd` docs and adds an extra example for both
`ngClassEven` and `ngClassOdd` that showcases animations.

Closes #15654