function percentDelta(uint256 a, uint256 b) internal pure returns (uint256)function percentDelta(int256 a, int256 b) internal pure returns (uint256)Returns the difference between two numbers in percentage, where 1e18 is 100%.
More precisely, percentDelta(a, b) computes abs((a-b) / b) * 1e18.
uint256 percent150 = stdMath.percentDelta(uint256(125), 50);
uint256 percent60 = stdMath.percentDelta(uint256(50), 125);