feat(scheme preview): Improved the schemes preview HTML page
feat(scheme preview): Improved the schemes preview HTML page

Improved the HTML page where you preview schemes. I tried to draw some inspiration from the mock
design.

base16-builder/base16-builder,aloisdg/base16-builder,aloisdg/base16-builder,base16-builder/base16-builder,base16-builder/base16-builder,aloisdg/base16-builder