This is the interface for storage miners to increase staking.
// IncreaseCollateral increases the number of staking for storage miner
// - accountID: storage miner account
// - token: number of staking
//
// Return:
// - string: block hash
// - error: error message
//
// Note:
// - The number of staking to be added is calculated in the smallest unit,
// if you want to add 1CESS staking, you need to fill in "1000000000000000000"
func (c *ChainClient) IncreaseCollateral(accountID []byte, token string) (string, error)