VWAP with editable Volume Time Frame

1. This custom indicator is based on TradingView VWAP preset indicator.
2. I added this line input("D", type=input.resolution, title="Time Frame") so I can adjust the time frame for the calculation of VWAP
3. The original VWAP setting is set at "D" while in this custom indicator, we can choose which time frame we prefer to suit our trading style.