Update options page with new styling and radio

[mirdaki]

I've pulled styling information from https://github.com/microsoft/vscode-webview-ui-toolkit. It's a rough approximation, since pulling in the library would require some kind of build system

I've switched to radio buttons for a simple experince and is the recommended approach for just a few items according to the VSCode guidelines from the webview library

This also fixes the flicker issue from #21

[mirdaki]

This is the new options look