font-optical-sizing figure should have a toggle, not 2 radio buttons

[davelab6]

On the font-optical-sizing figure, I'd like a toggle with a fixed position, not 2 radio buttons, so I can click and click again without moving the pointer to toggle it on and off.

[jpamental]

Started work on this in a new branch but ran in to issues with the CSS not compiling, and not quite sure how to fix it. Hoping @kennethormandy might have some insights. All the work is in this branch, and a test component has been added to the first Italic embed.

f3caed9