feat(transformers): add transformerRenderLineNumber

[dahiya001rohit]

• Implement transformerRenderLineNumber to inject line numbers as HTML elements.
• Support customization options: classLineNumber and startNumber.
• Export the new transformer in the main index file.
• Add unit tests to verify functionality.

#1201

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[Copilot]

Pull request overview

This PR adds a new transformer transformerRenderLineNumber that injects line numbers as HTML elements into syntax-highlighted code blocks. The transformer allows developers to visually display line numbers alongside their code, with customization options for the CSS class name and starting line number.

• Implements transformerRenderLineNumber with configurable classLineNumber and startNumber options
• Adds comprehensive unit tests covering basic functionality, custom classes, and custom start numbers
• Exports the new transformer in the package index

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 2 comments.

File	Description
packages/transformers/src/transformers/render-line-number.ts	New transformer implementation that prepends line number spans to each code line
packages/transformers/src/index.ts	Exports the new transformer in alphabetical order with other transformers
packages/transformers/test/render-line-number.test.ts	Unit tests covering basic usage, custom class names, and custom start numbers
packages/transformers/test/snapshots/render-line-number.test.ts.snap	Snapshot tests validating the HTML output for all test cases

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[Copilot]

For consistency with other transformers in this codebase (e.g., render-indent-guides.ts, meta-highlight-word.ts), use class instead of className in HAST element properties. Both work, but class is the convention used throughout this codebase.

class: classLineNumber,

Suggested change

	className: [classLineNumber],
	class: [classLineNumber],

[Copilot]

The as Text type assertion is unnecessary. The object literal already matches the Text type. Consider removing it for cleaner code:

children: [
  {
    type: 'text',
    value: `${number}`,
  },
],

Suggested change

	} as Text,
	},

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 95.22%. Comparing base (61c87e8) to head (769a09c).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1202      +/-   ##
==========================================
+ Coverage   95.20%   95.22%   +0.01%     
==========================================
  Files          92       93       +1     
  Lines        7922     7954      +32     
  Branches     1689     1694       +5     
==========================================
+ Hits         7542     7574      +32     
  Misses        374      374              
  Partials        6        6              

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