add a stable marker like a class name or data attribute to Box component

[radnan]

so folks (especially designers) can easily identify Axiom v2 components on a page visually

for example Axiom v1 uses the oui- prefix in their class names - so we could do something similar.

so someone could write a style rule in their web inspector adding a red outline to all Axiom v2 components to see how much of a page is using those components