auro-loader: support additional sizes xs and xxs

[jason-capsule42]

Is your feature request related to a problem? Please describe.

auro-loader needs to support smaller sizes for use in small elements such as auro-button.

Describe the solution you'd like

auro-loader should be able to scale all the way down to effectively appear inline with button text.

Describe alternatives you've considered

Could force auro-loader to scale using CSS transforms but it would be preferred to implement decorators for all sizes.

[blackfalcon]

Please open a DRAFT PR with this feature branch.

[blackfalcon]

@jason please remember to update the labels when the work status changes.