This commit modifies the theme creation process to include support for color themes. It adds a new checkbox field in the theme creation form to indicate whether the theme is a color theme. If the checkbox is selected, the CSS styles for the theme should be provided as a JSON object with the color values. Additionally, the `create-theme.yml` workflow file is updated to include the `THEME_IS_COLOR_THEME` environment variable when building the theme. The `rebuild-themes.py` script is also updated to generate a `chrome.css` file for color themes based on the provided color values in a `colors.json` file.
Fixes#69
