docs: add section about plugins options and improve examples in Motion UI docs

[ncoden]

Description

The current documentation about Motion UI is not clear enough about how to use the animation classes with the Foundation plugins that support it. A simple example is given for Toggler, and people may think that others components like Reveal can be used the same way (it does not, see to foundation/motion-ui#123).

This pull request add a section about the usage of Motion UI in the Foundation components with a list of the supported components and their options related to Motion UI. It also use a simpler example in the header section.

Changes

• Move Motion UI Toggler example to its own section
• Add a simpler example in Motion UI docs header

Screenshots (if appropriate):

Types of changes

• Documentation
• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing
  functionality to change)

Checklist (all required):

• I have read and follow the CONTRIBUTING document.
• There are no other pull request similar to this one.
• The pull request title is descriptive.
• The template is fully and correctly filled.
• The pull request targets the right branch (develop or develop-v...).
• My commits are correctly titled and contain all relevant information.
• My code follows the code style of this project.
• I have updated the documentation accordingly to my changes (if relevant).
• I have added tests to cover my changes (if relevant).
• All new and existing tests passed.

[DanielRuf]

better =)