Added Kotlin AST parser support

[deepaknlwl]

Description

This PR adds Kotlin language support to the Refact.ai AST parser, enabling code understanding and symbol extraction for Kotlin projects.

Impact

This implementation enables:

• Code Lens Feature: Code lens now works for Kotlin projects, providing buttons to Add in Chat, Find Problem and Explain
• @definition Support: Users can now use the "@definition" feature to navigate to symbol definitions in Kotlin code
• Improved LLM Context: Better context preparation for LLM interactions by providing accurate AST-based code understanding for Kotlin files
• Symbol Extraction: Full support for extracting classes, functions, properties, and other symbols from Kotlin source files

Fixes #906