Implement v4 API functions for Deposit about btcde

[CosmicDuck]

Hi, I added a new short function in the definition for showDeposits which is working well for the moment. I have no playing experience with github so here is my code which I inserted before showAccountInfo() procedure:

`
showDeposits()

def showDeposits(self, currency, **args):
    """Query on Deposits."""
    params = args
    avail_params = [ 'deposit_id', 'page' ]
    uri = f'{self.apibase}{currency}/deposits'
    p = ParameterBuilder(avail_params, params, uri)
    return self.APIConnect('GET', p)

`

[peshay]

Can you create a PR for it, with a unit test and documentation about that function in the README?