UI supporting HTML and CSS files

[benoit74]

In addition to one single HTML file, the UI must also support an HTML file and a CSS file.

We can for instance focus on https://www.freecodecamp.org/learn/2022/responsive-web-design/learn-the-css-box-model-by-building-a-rothko-painting/step-8

Note that by default only one of the two files are displayed, and focus is properly placed on the file needing an edit (the one with a --fcc-editable-region-- section)

Checklist

• Both HTML file and CSS file are displayable
• It is possible to see both side-by-side
• It is possible to resize them with a slider
• UI is responsive (one breakpoint / two dispositions: for mobile and desktop)
• Changes in CSS file are visible in preview pane
• Files are properly named
• It is possible to validate the challenge only with valid code ; hints are properly displayed next to the button and in the console