Bug Fixes/Enhancements:

- Added the chart.spinner method, which when set to `True` shows a loading spinner on the chart (a nice visual for API calls, large datasets etc).
- If an empty data frame is passed to set (eg.`chart.set(pd.DataFrame())`) the volume series and candle series will be cleared.
- added the `cumulative_volume` parameter to `update_from_tick`, which adds the given volume tick onto the latest bar.
- Added `vert_visible` and `horz_visible` parameters to `crosshair`.
- Small style improvements to the searchbox and topbar.
- Fixed a bug preventing callbacks within `WxChart` and `QtChart`

Thanks to @emma-uw for the following fixes and enhancements!
- Methods `hide_data`, `show_data`  and `price_line` can be used within Charts, Subcharts and Lines to change the visibility of data, price lines, and the price line labels.
- Added the `delete` method to Line, which irreversably deletes the Line on the chart as well as its objects in JavaScript and Python.
- Added the `lines` common method, which returns a list of all Line objects for the chart.
- Added the `fit` method to the common methods, which uses the `fitContent()` method from Lightweight Charts.
- Fixed a big which caused synced SubCharts to be out of sync upon loading.

BETA: Polygon.io integration
- Added the `PolygonChart` and `polygon` method, allowing for direct integration of polygon.io’s API.
- This feature is still in beta, and there will be a full announcement and update once the feature is complete!

lightweight_charts/util.py

@@ -1,3 +1,4 @@
+import re
 from random import choices
 from string import ascii_lowercase
 from typing import Literal
@@ -73,4 +74,20 @@ def _marker_position(p: MARKER_POSITION):
         'below': 'belowBar',
         'inside': 'inBar',
         None: None,
-    }[p]
+    }[p]
+
+
+def _convert_timeframe(timeframe):
+    spans = {
+        'min': 'minute',
+        'H': 'hour',
+        'D': 'day',
+        'W': 'week',
+        'M': 'month',
+    }
+    try:
+        multiplier = re.findall(r'\d+', timeframe)[0]
+    except IndexError:
+        return 1, spans[timeframe]
+    timespan = spans[timeframe.replace(multiplier, '')]
+    return multiplier, timespan