MarketChartData constructor
Constructs a MarketChartData instance with the given date and optional price, market capitalization, and total volume.
date - The date of the market data.
price - The price of the asset at the given date.
marketCap - The market capitalization of the asset at the given date.
totalVolume - The total volume of the asset traded at the given date.
Implementation
MarketChartData(
  this.date, {
  this.price,
  this.marketCap,
  this.totalVolume,
});