Added solution for Valid Parenthesis problem

[Sidhesh-Goud]

The isValid function checks if the input string s, which consists of parentheses, brackets, and braces, is valid. A string is considered valid if every opening bracket has a corresponding closing bracket in the correct order.
Parameters:
s (string): A string consisting of the characters (, ), {, }, [ and ].
Returns:
boolean: Returns true if the string is valid otherwise, returns false.

Logic:
Initialization:

• A mapping object elts is created to hold pairs of opening and closing brackets.
• An empty array stack is initialized to keep track of the opening brackets encountered in the string.

Iteration through the string:

• The function iterates through each character in the string s.
• If the character is an opening bracket (i.e., it exists in the elts object), it is pushed onto the stack.
• If the character is a closing bracket:
• The function first checks if the stack is empty. If it is, it means there's no matching opening bracket, and the function returns false.
• If the stack is not empty, the function pops the top element from the stack (the last opening bracket) and checks if it matches the current closing bracket. If it does not match, the function returns false.

Final Validation:

• After iterating through all characters, the function checks if the stack is empty. If it is empty, all opening brackets had matching closing brackets, and the function returns true. If not, it returns false.

Example:

• console.log(isValid("()")); // true
• console.log(isValid("()[]{}")); // true
• console.log(isValid("(]")); // false
• console.log(isValid("([)]")); // false
• console.log(isValid("{[]}")); // true