Contribute tags to gatsby-theme-carbon

[elycheea]

From issue https://github.com/carbon-design-system/carbon-for-products-website/issues/76 After previous discussion with @szinta @alisonjoseph @ljcarot, think it would make more sense to contribute to this the theme otherwise it may require us to shadow the nav.

Waiting for tree nav to be completed before we work on this!

### Tasks
- [ ] Design spec needed
- [ ] Determine what this looks like in the yaml file?

[szinta]

@aubrey-oneal / @oliviaflory Could you please share the Figma link for the design spec of the Tag components in the Side nav?

[oliviaflory]

Hi @sintaibm let's hold off on this for now. I haven't created a design spec and would need to run it by the other designers before starting this work