Add updated styling for the resize button on the Viewer component

[janechu]

Description

Add updated styling for the resize button on the <Viewer /> component in the @microsoft/fast-tooling-react package.

Requirements

• Create a design with the Viewer that showcases a new button in the bottom right corner
• Add a the design below

Design

Follow up

Create an issue for completing the development work in <Viewer />.

The issue should contain:

• The removal of the bottom left resize button
• Updated styling as per this issue
• The removal of styling for the scrollbars