fix: a page in the dark color scheme, also one in an iframe, is no longer white while it loads, and test-container.mjs runs the checks with Docker.

package.json

@@ -1,7 +1,7 @@
 {
   "name": "@koszewscy/sk-react-toolkit",
-  "version": "0.7.0",
-  "description": "Shared code of the React and Fastify web applications: web components, server helpers and the Vite font plugin.",
+  "version": "0.7.1",
+  "description": "Shared code of the React and Fastify web applications: web components, server helpers and the Vite font and color scheme plugins.",
   "private": true,
   "type": "module",
   "engines": {