feat: add Dart syntax highlighting for the code blocks in the editor (#5531)

添加代码块 dart 语言的高亮

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#### What type of PR is this?
/kind feature
/area editor

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#### What this PR does / why we need it:
> 为默认编辑器的代码块导入 dart 语言高亮
#### Which issue(s) this PR fixes:
Fixes #5530 
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#### Special notes for your reviewer:

#### Does this PR introduce a user-facing change?

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```release-note
为需要代码块dart语言高亮的用户提供支持
```

ui/packages/editor/src/extensions/code-block/lowlight.ts

@@ -1,6 +1,8 @@
 import { common, createLowlight } from "lowlight";
 import xml from "highlight.js/lib/languages/xml";
+import dart from "highlight.js/lib/languages/dart";
 
 const lowlight = createLowlight(common);
 lowlight.register("html", xml);
+lowlight.register("dart", dart);
 export default lowlight;