Add subplot example for reference when using plotly dash

subplot_example.py

@@ -0,0 +1,29 @@
+from database.ohlc import ohlc
+from datetime import datetime, timedelta
+
+from candlestick_chart import CandlestickChart
+from line import Line
+from line_chart import LineChart
+from plot import figure_with_subplots
+
+end_date = datetime.today().date()
+start_date = (end_date - timedelta(days = 90))
+data = ohlc('SPX.XO', '1d', start_date = start_date, end_date = end_date)
+
+candlestick_chart = CandlestickChart(
+    x = data['Timestamp'], 
+    opens = data['Open'], 
+    highs = data['High'], 
+    lows = data['Low'], 
+    closes = data['Close'],
+    title = 'SPX'
+)
+
+line_chart = LineChart(
+    x = data['Timestamp'], 
+    lines = [Line(data['Close'], name = 'Close')],
+    title = 'SPX (Close)'
+)
+
+# For use in plotly dash.
+figure_with_subplots([[candlestick_chart], [line_chart]]).show(config = {'displayModeBar': False})