Added backadjustment parameter to session.js, this will allow to define if futures contracts should be backadjusted in terms of roll yield or not

Author: Svetozar Korytiak

src/chart/session.js

@@ -331,6 +331,7 @@ module.exports = (client) => class ChartSession {
    * @param {number} [options.range] Number of loaded periods/candles (Default: 100)
    * @param {number} [options.to] Last candle timestamp (Default is now)
    * @param {'splits' | 'dividends'} [options.adjustment] Market adjustment
+   * @param {boolean} [options.backadjustment] Market backadjustment of futures contracts
    * @param {'regular' | 'extended'} [options.session] Chart session
    * @param {'EUR' | 'USD' | string} [options.currency] Chart currency
    * @param {ChartType} [options.type] Chart custom type
@@ -350,6 +351,7 @@ module.exports = (client) => class ChartSession {
       adjustment: options.adjustment || 'splits',
     };
 
+    if (options.backadjustment) symbolInit.backadjustment = 'default';
     if (options.session) symbolInit.session = options.session;
     if (options.currency) symbolInit['currency-id'] = options.currency;