Issue: #74

Description:
This pull request extends the showLineNumbers option from a boolean to boolean | string[]. Currently, setting showLineNumbers to true displays line numbers for all code blocks that include the meta property 'showLineNumbers'. With this change, you can specify an array of languages (e.g., ['typescript']) to show line numbers only for those languages. Other languages, like plain text, will not display line numbers.

Changes:

• Type Update: Change showLineNumbers type from boolean to boolean | string[].
• Logic Modification: Update the line numbering logic to check if showLineNumbers is an array. If it is, only add line numbers for code blocks whose language is included in the array.
• Documentation: Update docs and examples to reflect the new functionality.

Usage Examples:

// Display line numbers for all code blocks
showLineNumbers: true

// Display line numbers only for code blocks with the 'typescript' or 'java' language
showLineNumbers: ['typescript', 'java']