feat(icon component): Adds an Icon component along with corresponding CSS styles

[janiekyu]

Changes in this PR:

• Added new Icon component. In React we can specify Skippy or other select Phosphor icons. In Core, we can include any Phosphor icon by using the Phosphor icon name.
• Switched from phosphor-react package to @phosphor-icons/react as recommended by Phosphor and to get access to new icons.
• Updated existing snapshots that include Phosphor icons as the SVG code changed

Storybook previews:

• REACT: https://dev--designwithcompassion.netlify.app/storybook/react/?path=/docs/components-icon--docs
• CORE: https://dev--designwithcompassion.netlify.app/storybook/core/?path=/docs/components-icon--docs

[janiekyu]

Snapshot diffs are related to the new Icon component and updates to the Phosphor icon library.