Carbon: [icon button] add ghost icon button functionality to react

[laurenmrice]

We need to add a ghost icon button. This type of button is being used a lot within UIs when it's not the primary call to action on the page (provisioning experiences, options within a data table row @marceltrautmann ). The icon needs to have a default icon-01 color with the option to switch to icon-02 as well.

---

Spec:

[tw15egan]

This should already exist, but let me know if we're missing something:

(knobs --> button kind --> ghost)
https://react.carbondesignsystem.com/?path=/story/buttons--icon-only-buttons

[laurenmrice]

Yeah I think we just want to not have the icon blue by default for the icon only button and have a icon-01 and icon-02 option.

People are using these throughout their designs and we recommend they use these token values for this kind of button rather than always using blue.

[tw15egan]

Okay, so for icon only ghost buttons, we want it to always be icon-01? We can update the styles so that it defaults to that instead of blue when it is just the icon.

[laurenmrice]

correct!

[tw15egan]

PR incoming 🚀