iOS: Action asset back icon

[Harris Borawski]

Depends on #169

In the iOS reference action asset

• Render a < icon next to the label based on metaData.role
• Do not render a button background when rendering the back icon, instead apply the background color to the text

[aarianasingh]

Hi! Can I work on this issue?

[pratyushajog]

Hi @hborawski, Can I work on this?