feat: Adding CSharp Snippets

[chaitanya-jvnm]

Description

Added c# Utilities for the following:

• String Utilities: Capitalize the first character of string
• GUID Utilities - Create, decode and Validate GUID
• JWT Utilities - Create, decode and Validate JWT

Type of Change

• ✨ New snippet
• 🛠 Improvement to an existing snippet
• 🐞 Bug fix
• 📖 Documentation update
• 🔧 Other (please describe):

Checklist

• I have tested my code and verified it works as expected.
• My code follows the style and contribution guidelines of this project.
• Comments are added where necessary for clarity.
• Documentation has been updated (if applicable).
• There are no new warnings or errors from my changes.

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[Mathys-Gasnier]

Hey, thanks for the contribution, please take a look at the comment i left before we can move on with your snippets.
Also, please include examples of use in your snippets, take a look at other snippets to see how to do it !