[spike] Research the guidance provided by other design systems on tokens

[GCHQ-Developer-112]

This ticket details the pre-work for https://github.com/mi6/ic-design-system/issues/1662

Why do we need it?

This ticket involves researching how our design systems explain their design tokens and look for what we think will work for our design system. Ticket https://github.com/mi6/ic-design-system/issues/1662 will likely be a big undertaking.

A good example is Atlassian