Option to toggle component sizes on demo pages

[FlyersPh9]

As we are starting to add more sizes to most of our components it would be nice to have a row of links underneath the demo page, similar to this:

This would cut down on the amount of components per demo page. In some cases like text field I could see this being very nice.

Two issues i foresee with this:

1. Testing: we would need tests to run 3x to capture all the different sizes separately.
2. Nested objects: the text field with a borderless button right aligned within it. if the text field changes to .iui-large the button also needs that class appended, not just the text field.

[maxime4000]

I made this month ago, would be nice to see it come to life.