The var-name-mixedcase rule triggers when using $ as a variable name

[ernestognw]

Description

Given Solidity allows using a $ as a valid variable identifier, consider the following example:

contract A {
    function example() external pure returns (uint256) {
        uint256 $ = 1;
        return $;
    }
}

The variable $ is marked as Linter: Variable name must be in mixedCase [var-name-mixedcase].

Proposed solution

The library should not throw an error when the variable includes a $

[dbale-altoros]

This is solved in this PR
#465