feat/TMR-2874-Allow-mui-icons

[KayKostadinov]

Jira- TMR-2874

What
Extend the interface of toNewskitIcon function to allow 3rd party icon libraries

I have done:

• Written unit tests against changes
• Written functional tests against the component and/or NewsKit site
• Updated relevant documentation

I have tested manually:

• The feature's functionality is working as expected on Chrome, Firefox, Safari and Edge
• The screen reader reads and flows through the elements as expected.
• There are no new errors in the browser console coming from this PR.
• When visual test is not added, it renders correctly on different browsers and mobile viewports (Safari, Firefox, small mobile viewport, tablet)
• The Playground feature is working as expected

Before:

After:

Who should review this PR:

How to test: