feat(core/button) loading state

[goncalosard]

Pull request checklist

Please check if your PR fulfills the following requirements:

• Tests for the changes have been added (for bug fixes / features)
• Docs have been reviewed and added / updated if needed (for bug fixes / features)
• Build (yarn build) was run locally and any changes were pushed
• Unit tests (yarn test) were run locally and passed
• Visual Regression Tests (yarn visual-regression) were run locally and passed
• Linting (npm lint) was run locally and passed

Pull request type

Please check the type of change your PR introduces:

• Bug fix
• Feature
• Refactoring (no functional changes, no API changes)
• Build related changes
• Documentation content changes
• Other (please describe):

What is the current behavior?

[IX-250]

What is the new behavior?

• Added loading button example to Button documentation

Does this introduce a breaking change?

• Yes
• No

[goncalosard]

@nuke-ellington @danielleroux New loading button was added with the new props. Documentation examples were also added.
No VRT was added because of moving spinner, making it always fail.

[danielleroux]

Changed the PR to a breaking change.

I have replaced the spinner animation with a new one which fits better into the library. Final adaptions regarding the animation will be done maybe later on.

Removed the type from the interface of the spinner

Add a breaking change section to the document.

[nuke-ellington]

lgtm