Add multi-language template support

[thirteen7]

This update introduces multi-language template support for Competitive Programming Helper (CPH).

Changes include:

• Added a function to get language-specific template file locations.
• Companion extension now applies templates based on the user's selected programming language.
• Falls back to the global default template if a language-specific template is not found.
• Supports popular languages including C, C++, Java, Python, JavaScript, Go, Rust, Ruby, Haskell, and C#.
• Ensures proper application of templates for Java classes (replaces CLASS_NAME dynamically).
• Handles missing or invalid template paths gracefully with informative error messages.

This enhancement improves the workflow for users who solve problems in multiple languages, allowing templates to be applied automatically per language.