App Style Editor UI

Background Plotly Studio users don't often know how to write CSS themselves, and struggle to use DDK effectively because it requires manual code to be written in a theme.js file and is not user-friendly. While Plotly Studio offers a "Custom" theme, users have reported that this is too limited for their needs.

Problem Plotly Studio users need an easier, and more granular way to define the style of their app. Ideally users should be able to affect styles interactively and see the preview instantaneously. Early Requirements Users need to be able to define: - Colors: - Primary, secondary, etc. colors - Default chart color palette (can be overridden by chart configurations) - Fonts - Font face - Sizes - Layout spacing - Rounded vs. sharp corners - Table styles - Alternating backgrounds - Spacing - Column summaries On\/Off