Create internal function to check user token balance for swap

[Akshola00]

Goal

Develop an internal function that verifies if a user holds enough of the specified ERC-20 token for swapping on the DEX.

Requirements

• The function should take the user’s address, the ERC-20 token’s contract address, and the amount of tokens the user wants to swap as parameters.
• Using the ERC-20 contract address, get an instance of the token.
• Check the user's token balance to ensure they have the required amount.
• Return a boolean value indicating whether the user has enough tokens to complete the swap.