message: fix: support an old customize-manifest.json format
diff: @@ -150,6 +150,9 @@ export const run = async (
  updated: false
  };
  + // support an old format for customize-manifest.json that doesn't have mobile.css
  + manifest.mobile.css = manifest.mobile.css || [];
  +
  const files = manifest.desktop.js
  .concat(manifest.desktop.css, manifest.mobile.js, manifest.mobile.css)
  .filter((fileOrPath: string) => !isUrlString(fileOrPath));
  