Enhanced Template Java class name substitution

[KshKnsl]

Fixing #512

Key Enhancement:

Auto-Class Naming for Java:
When creating a new Java file via Competitive Companion, the placeholder CLASS_NAME in the Java template is automatically replaced with the problem's name.
This ensures that the Java class name matches the problem name, complying with Java's requirement for public class names to match the filename.

Testing Instructions:

Ensure your Java template includes CLASS_NAME as a placeholder for the class name.
Use Competitive Companion to create a new Java file.
Verify that the generated file replaces CLASS_NAME with the problem name correctly.

Additional Notes:

This feature is specific to Java but can be adapted for other languages with similar requirements.
Also for non template file, we can have some boiler for each language.

[AgX111]

This is such a QOL for Java users!