Added Infix to Postfix Conversion

[twinkle485]

PR Description:

Summary:

This PR adds a C program to convert an infix expression to a postfix expression using a stack. The program handles operator precedence, parentheses, and alphanumeric operands.

Changes:

• File Added: InfixToPostfix.c
• Implemented push(), pop(), peek(), precedence(), isOperator(), and infixToPostfix() functions.

How to Test:

1. Compile and run infix_to_postfix.c.
2. Example input: (A+B)*C
   • Output: AB+C*

Additional Notes:

• Supports basic operators: +, -, *, /, and ^.
• Currently assumes no spaces in the input.