Polygon:

- Added async methods to polygon.
- The `requests` library is no longer required, with `urllib` being used instead.
- Added the `get_bar_data` function, which returns a dataframe of aggregate data from polygon.
- Opened up the `subscribe` and `unsubscribe` functions

Enhancements:
- Tables will now scroll when the rows exceed table height.

Bugs:
- Fixed a bug preventing async functions being used with horizontal line event.
- Fixed a bug causing the legend to show duplicate lines if the line was created after the legend.
- Fixed a bug causing the line hide icon to persist within the legend after deletion (#75)
- Fixed a bug causing the search box to be unfocused when the chart is loaded.

docs/source/examples/yfinance.md

@@ -0,0 +1,48 @@
+# YFinance
+
+```python
+import datetime as dt
+import yfinance as yf
+from lightweight_charts import Chart
+
+
+def get_bar_data(symbol, timeframe):
+    if timeframe in ('1m', '5m', '30m'):
+        days = 7 if timeframe == '1m' else 60
+        start_date = dt.datetime.now()-dt.timedelta(days=days)
+    else:
+        start_date = None
+
+    chart.spinner(True)
+    data = yf.download(symbol, start_date, interval=timeframe)
+    chart.spinner(False)
+
+    if data.empty:
+        return False
+    chart.set(data)
+    return True
+
+
+def on_search(chart, searched_string):
+    if get_bar_data(searched_string, chart.topbar['timeframe'].value):
+        chart.topbar['symbol'].set(searched_string)
+
+
+def on_timeframe_selection(chart):
+    get_bar_data(chart.topbar['symbol'].value, chart.topbar['timeframe'].value)
+
+
+if __name__ == '__main__':
+    chart = Chart(toolbox=True, debug=True)
+    chart.legend(True)
+    chart.events.search += on_search
+    chart.topbar.textbox('symbol', 'n/a')
+    chart.topbar.switcher(
+        'timeframe',
+        ('1m', '5m', '30m', '1d', '1wk'),
+        default='5m',
+        func=on_timeframe_selection
+    )
+
+    chart.show(block=True)
+```