Docusaurus: Dart Code is not colorizing in browser.

[yahu1031]

🐛 Bug Report

```dart title="main.dart"
import 'dart:html';

void main() {
var header = querySelector('#header');
header.text = "Hello, World!";
}
`` This doesn't recognize dart language, where as if I make it asjava` it does give the code colors.

Have you read the Contributing Guidelines on issues?

yes

To Reproduce

(Write your steps here:)

1. Write some dart code and check the code with dart and java code block
   
   
2. Check in the browser.

Expected behavior

I want that code to be colored when I use ```dart.

Actual Behavior

Your Environment

• Docusaurus version used:
  json "dependencies": { "@docusaurus/core": "2.0.0-alpha.66", "@docusaurus/preset-classic": "2.0.0-alpha.66", "@mdx-js/react": "^1.5.8", "clsx": "^1.1.1", "react": "^16.8.4", "react-dom": "^16.8.4" },

• Environment name and version (e.g. Chrome 78.0.3904.108, Node.js 10.17.0):

  Microsoft Edge is up to date.

  Version 86.0.622.69 (Official build) (64-bit)

  As microsoft edge is developed on chromium, hoping chrome or Edge doesn't make difference.

  Node JS

  v14.15.0

• Operating system and version (desktop or mobile):

  Edition Windows 10 Pro
  Version 20H2
  Installed on ‎18-‎11-‎2020
  OS build 19042.630
  Experience Windows Feature Experience Pack 120.2212.31.0

Reproducible Demo

[Simek]

Hi @yahu1031,

you need to add Dart to the Prism additionalLanguages configuration field:

themeConfig: {
    prism: {
      additionalLanguages: ['dart'],
    },
}

You can read more about syntax highlighting features and configurtation in the docs:

• https://v2.docusaurus.io/docs/markdown-features/#syntax-highlighting

Result

[yahu1031]

@Simek Thanks for the help ❤️