Calculate how many liquidity tokens we should be minting to send back to the
user when adding liquidity. We provide new liquidity equal to the existing
liquidity multiplied by the ratio of new central tokens to central tokens
already held. If the current supply is zero, return the inputValue as the
initial liquidity to mint is arbitrary.
Calculate how many liquidity tokens we should be minting to send back to the user when adding liquidity. We provide new liquidity equal to the existing liquidity multiplied by the ratio of new central tokens to central tokens already held. If the current supply is zero, return the inputValue as the initial liquidity to mint is arbitrary.