feat: add build:test script and improve documentation code blocks

- Added a new script `build:test` to generate test cases from documentation code examples.
- Enhanced documentation files by ensuring proper code block formatting and adding missing closing backticks.
- Updated various markdown files to include new code blocks and fixed formatting issues.

packages/artplayer-vitepress/docs/en/advanced/plugin.md

@@ -121,4 +121,5 @@ var art = new Artplayer({
             url: '/assets/sample/layer.png'
         })
     ],
-});
+});
+```